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Director, New York State School of Agriculture 
at Alfred University. Formerly Assist- 
ant Professor of Horticulture at the 
Pennsylvania State College 







19 17 


Copyright, 1917, by 

All Rights Reserved 

Entered at Stationers* Hall 
London, England 

Printed in U. S. A. 







In 1912 the author was asked to present a 
paper before the National Vegetable Grow- 
ers' Association on the construction and 
equipment of greenhouses, with special refer- 
ence to the vegetable forcing industry. Much 
of the data given in this paper had been 
hitherto unavailable and was based on an 
extensive personal survey of greenhouse 
owners and operators, supplemented by per- 
sonal experience and observation. So great 
has been the demand for this data that at the 
request of the Orange Judd Company, the 
author has undertaken to incorporate it in 
book form. The present volume attempts 
a more thorough discussion of the subject 
than could be given in a single paper. It 
is based upon a series of lectures given be- 
fore the author's classes. 

This is the second book, dealing exclu- 
sively with this subject, which has been pub- 
lished in the United States. The former, 
written by Prof. L. R. Taft and published by 



the Orange Judd Company in 1893, has been 
the standard and only work devoted entirely 
to greenhouse construction as adapted to 
American conditions. To this and to Pro- 
fessor Taft the author of the present volume 
is deeply indebted. It is not intended that 
this second bbok shall supersede the former 
but that it shall supplement it and emphasize 
present-day features. Probably in no line of 
horticulture has so great progress been made 
in the past quarter of a century as in floricul- 
ture and vegetable forcing. The develop- 
ment of the forcing house has been no less 

No attempt has been made to discuss the 
question of greenhouse construction from the 
standpoint of the manufacturer, although 
due credit must be given to the energy and 
ingenuity v\^hich he has displayed in meeting 
the rapidly changing conditions and in the 
excellence of present-day construction. It 
is probably not too much to say, that the 
development of the flower and vegetable 
forcing industry has been largely dependent 
upon the improvement vsrhich has been made 
in the manufacture of greenhouse material 
and equipment. 

The real purpose of the book is to pre- 


sent to the reader such information con- 
cerning the location, adaptation, general con- 
struction and equipment of greenhouses as 
will enable him to decide upon the type of 
house best adapted to his special needs; to 
supervise or assist if need be in its construc- 
tion or erection; to arrive at some conclu- 
sion as to the equipment most likely to ren- 
der the service required, and the probable 
cost. A special effort has been made to make 
the volume of service to the present owner 
of a greenhouse and to those who may con- 
template building, whether it be a small 
private house or a large commercial range. 
The arrangement of topics is made with 
reference to a pedagogical system which 
it is. hoped will be of service to the teacher 
and student. 

It is practically impossible to give in- 
dividual credit for all the sources drawn up- 
on in the preparation -of this volume. Spec- 
ial mention should be made, however, of the 
assistance given by the manufacturers of 
greenhouse building material and for the 
many excellent illustrations which they have 
furnished. When practicable, the source of 
these illustrations is given. Free use has 
also been made of bulletins of the various 


Experiment Stations and of the United 
States Department of Agriculture. 

The book is offered with a full conscious- 
ness of its shortcomings, but with the hope 
that it may be of some definite service and 
that it may serve as a focusing point for 
criticisms and suggestions, out of which 
may be born a fuller knowledge through the 
experience and observation of its readers. 

W. J. Wright. 
New York State 
School of Agriculture, 1917, 
Alfred, New York. 


A General Survey 1-0 

Classes of sash-beds — Classes of green- 
houses — Evolution of the greenhouse. 


Sash-bed Construction .... 10-34 

Hotbeds, location of, sash, pit, manure for — 
Coldframes — Cold or storage pits — Forcing 
boxes — Gable roof sash-beds — Majts and 
shutters — Care of sash-bed materials. 

Greenhouse Proper — General Con- 
siderations 35-49 

Location — ^Arrangement — Size of houses — 
Pitch of roof — Measuring the pitch — Length 
of rafters. 

Greenhouse Architecture . . . 50-62 

Lean-to or shed-roof houses — Even-span or 
span-roof houses — Uneven span houses — 
Ridge-and-furrow houses — 'Side hill houses 
— Curved roof houses — Curved eave houses 
— Circular houses. 


Structural Material 63-79 

Glazing sill — Eave plate — Gutter — Glazing 
bars — Side posts — Sash bars — Gable bars — 
Drip gutters — Purlins — Ridge — Kinds of 
wood used — Framing. 




Framework, Methods of Erecting . . 80-96 
Cardinal virtues of a good greenhouse frame- 
work — Foundations and walls — Wood-frame 
houses — Semi-iron irame houses — ^All-metal 
frame houses. 


Glazing and Painting 97-120 

Greenhouse glazing an art — Glass tp use — 
Size of glass — Lapped glazing — Butted glaz- 
ing — Putty — Setting the glass — How to esti- 
mate putty — Glazing points — Precautions — 
Liquid putty — Substitutes for glass — Kind of 
paint — Amount of paint required — Shading 
— Glazing ladder. 


Ventilation and Ventilating 

Machinery 121-141 

Systems of greenhouse ventilation — Side 
ventilation — Overhead ventilation — Size of 
ventilators — Hanging ventilator sash — Venti- 
lator operating machinery — Shafting — Shaft 
hangers — Gearing — ^Ventilator arms — Capa- 
city of ventilating apparatus — Sliding shaft 


Beds, Benches and Walks . . . . 142-157 
Advantages and disadvantages of benches — 
JRaised beds — Wood benches — Iron frame 
benches — Concrete benches — Height and 
width of benches — Arrangement of benches 
and walks — Walks and curbs. 


Greenhouse Heating 158-166 

The principles of greenhouse heating — Heat- 
ing with flues — Hot water vs. steam heating 
— Combination heating systems — Heating 
coils — Cast iron and wrought iron pipes for 


Hot Water Installation .... 167-187 
General principles — Formula for determin- 
ing velocity of water in heating s_ystems — 
Estimating radiation — Amount of pipe re- 
quired — Size of flow pipe — Length of coils 
— Expansion tank — Pressure systems. 



3team Installation 188-199 

General principles — Size and length of coils 
— Size of supply and return pipes — Valves — 
High pressure steam heating — Vacuum and 
vapor systems — Arrangement of boilers — 
Steam pumps and steam traps. 


Boilers, Fuels and Flues .... 200-225 

Essentials of a boiler — Grate surface — Fire 
surface — Types of boilers — Cast and wrought 
iron boilers — Styles of cast iron boilers — 
Styles of wrought iron boilers — Steam and 
hot-water boilers — Boilers for burning hard 
and soft coal — Under-fed boilers — Self-stok- 
ing boilers — Size of chimneys and flues — 
Arrangement of flues. 

Water Supply and Irrigation . 

. 226-241 

Amount of water required — Types pf pumps 
— Capacity of pumps — Power required — 
Hydraulic rams — Capacity of rams — Wind- 
mills for pumping — Storage tanks— Capacity 
of storage tanks — Overhead irrigation — 

Concrete Construction 

. 242-256 

How concrete is made — Kind of sand re- 
quired — Kind of stone or gravel required — 
Crushed stone — How materials are propor- 
tioned — Directions for mixing — Amount of 
water required — Estimating materials — 
Forms for walls — Reinforcing — Walks and 
floors — Water-proofing — Concrete blocks — 
Cost of concrete work. 


Plans and Estimates 257-262 

Basis of estimate — Average costs—Detailed 
estimates — Information required in obtain- 
ing estimates. 



Conservatories, New» York Botanical Gardens 


1 Hotbed in operation 10 

2 Standard -hotbed sash 12 

3 Double-glass sash 15 

4 Plait for permanent hotbed . . . .19 

5 Permanent hotbed of concrete with cast-iron sills 19 

6 Plan for temporary hotbed . . . . .20 

7 Type of hotbed used when a large amount of 

heat is required . . . . . .20 

8 Usual type of concrete hotbed 21 

9 Hotbed arranged for heating by flues . . 23 

10 A good type of coldframe 24 

11 Coldframe with sash removed . . . .25 

12 A cold or storage-pit 26 

13 Sash-bed attached to basement of dwelling . 28 

14 Types of forcing boxes or plant forcers . . 29 

15 Forcing boxes in use on a commercial scale . 29 

16 Gable-roof sash-bed heated by manure . . 30 

17 Rye straw mats rolled for storage . . .31 

18 Hotbed covered with mat and shutter . . .32 

19 Private range of C. E. Chapman, Oakdale, N. J. . 37 

20 Ground plan of range shown in Fig. 19 . .38 

21 Commercial range of Hoerber Bros., DesPlaines, 

111 39 

22 Ground plan of range shown in Fig. 21 . .40 

23 Part of vegetable forcing range of Searls Bros., 

Toledo, Ohio .41 

24 Diagram showing method of measuring pitch of 

roof 42 

25 Commercial range of C. H. Metcalfe, Milford, 

Mass. 43 

26 Diagram showing how heat and light rays are 

lost by reflection . 44 

26a Diagram showing pitch of roof necessary to pre- 
sent an angle of 90 degrees to Jhe sun's rays 
in winter . . . •• . . .45 

27 An uneven span greenhouse . . . .53 

28 Uneven span, side-hill vegetable house . . 55 




29 Ridge-and-furrow houses wrecked by a storm . 57 

30 Diagram showing that the same amount of roof 

is required for several small, connected houses 

as for one large house covering the same area 58 

31 Diagram of side-hill range 60 

32 Curved-eave and circular types of construction . 61 

33 Two methods of framing a semi-iron frame 

greenhouse 64 

34 Types of sills 65 

35 Types of eave plates ....... 66 

36 Types of gutters . . . . . .67 

37 Type of gutter for curved-eave houses • . 68 

38 Cross section of corner bar . . , .68 

39 Types of wood sash bars . . . . .70 

40 Two types of patented metal sash bars • . 71 

41 King "Channel Bars'* 72 

42 ''U-Bar" type of sash bar . . . . . 72 

43 Gable rafter 73 

44 Combination eave plate and gutter . . .73 

45 Pipe strap for fastening sash bars to purlins . 75 

46 *Tecky" cypress . . . . . ,77 

47 The concentric system of construction . . 78 

48 A type of all-metal flat rafter construction . 81 

49 Plan for an all-wood frame greenhouse . . 85 

50 Two methods of framing a semi-iron frame 

house 89 

51 Structural steel post with board wall . . .90 

52 Section of truss-frame greenhouse . . .91 

53 Section of combination truss-frame greenhouse 92 

54 Method of erecting a large combination truss- 

frame greenhouse . . . . . .93 

55 Side view of house shown in Fig. 54 . . .95 

56 A method of erecting small all-metal frame 

houses . 96 

57 Lapped glazing 102 

58 Putty knife 104 

59 Machine for distributing putty . . . . 104 

60 A, window glazing; B, greenhouse glazing . . 105 

61 Putty bulb 108 

62 Types of glazing points . . . . . 109 

63 Glazing with double pointed glazing points . 110 

64 Glazing with single glazing points . ^ . .111 

65 Glazing ladder used in glazing and painting . 120 

66 Greenhouse showing A, side ventilators; B, over- 

head or roof ventilators ..... 123 

67 Method of under-bench ventilation . - . 125 

68 Two methods of hanging ventilator sash . . 127 



69 Malleable iron shaft coupling .... 129 

70 Shaft hangers . . . . * . . .130 

71 Open column ventilator gearing . . . 131 

72 Open column chain operated ventilator, gearing 131 
IZ Closed column ventilator gearing . . . 132 

74 Chain system of operating ventilators . . 133 

75 Rack-and-pinion system of operating ventilators .133 
Id Ventilators operated by means of rods with uni- 
versal joints ....... 135 

n Device for operating side ventilators . . . 136 

78 Compact machine for operating side ventilators 137 

79 Types of ventilator arms . . .138 

80 Sliding shaft system for operating ventilators . 141 

81 Cucumbers growing in ground, no benches used. 143 

82 Tomatoes growing in solid raised beds . . 145 

83 Solid raised beds of hollow building tile . . 145 

84 Two types of wood benches .... 147 

85 A type of iron frame bench .... 148 

86 Greenhouse bench of concrete . . . .150 

87 Method of arranging benches in an uneven span 

house ........ 153 

88 An arrangement of benches in a 30 foot house . 154 

89 Another arrangement of benches in a 30 foot 

house 155 

90 A combination steam and hot water heating 

system . . . . . . . 162 

91 Under bench heating with large cast iron pipes . 165 

92 Diagram showing "down hill" and "up hill** sys- 

tems of hot water piping . ... 170 

93 A type of automatic air valve .... 171 

94 A method of piping a medium size house . . 178 

95 Diagram showing under-bench method of hot 

water piping . 179 

96 Gasoline engine arranged to circulate hot water 

in a greenhouse heating system . . . 180 

97 Automatic expansion tank ...... 182 

98 A type of mercury "generator" .... 185 

99 A corner coil 191 

100 A mortise coil 192 

101 Reducing valve ....... 195 

102 A type of steam return trap .... 199 

103 A type of "vertical" or "square** sectional boiler 204 

104 End view of "square" sectional boiler showing 

fire travel 205 

105 Side view of "square" sectional boiler showing 

fire travel 206 

106 Battery of five cast iron sectional boilers . . 207 



107 A type of **round'* or "horizontal" sectional 

boiler 208 

108 Corrugated fire box boiler ..... 209 

109 Type of tubular boiler much used in greenhouse 

heating 210 

110 Battery of two marine type boilers used in green- 

house heating 211 

111 Wrought iron boiler without flues . . . 212 

112 Sectional view of boiler shown in Fig. Ill . . 213 

113 Altitude guage 215 

114 Water column and guage ..... 216 

115 Steam guage 217 

116 Diagram of automatic damper regulator . . 217 

117 Asbestos pipe covering ..... 218 

118 Boiler equipped for using natural gas . . 219 

119 Chimneys should extend above the roofs of ad- 

jacent buildings . . . * . . . 224 

120 Pumping jack 227 

121 Diagram showing installation of auto-pneu- 

matic pump ....... 228 

122 A simple type of hydraulic ram .... 232 

123 Plan for installing a hydraulic ram . . . 233 

124 Overhead irrigation- ...... 239 

125 A type of nozzle used in overhead irrigation . 240 

126 Greenhouse bench arranged for sub-irrigation . 241 

127 Proportions of cement, sand and §tone required 

to form concrete ...... 245 

128 Form for a concrete wall 250 

129 Method of facing a concrete wall . . . 251 

130 Structure of a concrete walk . ' . . . 253 

131 A small power machine for mixing concrete . 255 



It is not the purpose of this book to furnish 
detailed information concerning the manu- 
facture of greenhouse building material, for 
the cutting and shaping of the materials is 
the work of the mill and the factory. Its 
purpose is rather to present such informa- 
tion concerning the location, adaptation, 
erection and equipment of greenhouses as 
will enable the reader to decide upon the type 
of house best adapted to his special needs ; to 
supervise or assist if need be, in its construc- 
tion or erection; and to arrive at some con- 
clusion as to the equipment most likely to 
render the service required. 

Greenhouses are the result of an attempt 
on the part of man to create conditions favor- 
able to the growth of plants in climates or 
during seasons naturally unfavorable. They 
must, therefore, protect the plants from cold 
and storms, allow for an abundance of direct 
sunlight, provide for ventilation and in most 


'g:'*L--:V •••••.•iSfefcENHOUSES 

cases they must be equipped with facihties 
for artificial heating. 

In a general sense, the term greenhouse re- 
fers to those glass structures used for the 
growing of plants. They are for the most 
part above ground and are house-like in ap- 
pearance. There is, however, another gener- 
al class of glass structures also used for the 
growing^ of plants but which are low and 
often almost wholly under ground. Unfor- 
tunately, there is no general term commonly 
applied to them as a class, but since it is 
common to use in their construction certain 
standard-size glass sash, the author ventures 
to suggest the term sash-bed as a general 
one to include structures of this class ; and it 
is so used in this book. 


Hotbeds. — These are low structures, being 
almost wholly under ground, but having a 
glass roof made up of sash which are of con- 
venient size to be lifted off, so that the grow- 
er may care for the plants. They are usually 
warmed by the heat generated by decaying 
vegetable matter, commonly horse manure. 

*For details see Chapter II. 


Their chief use is for starting plants in early 

Coldframes. — These are similar to hotbeds 
but are seldom heated and may therefore be 
of more shallow construction, as no pit is 
needed to store the manure. Their chief use 
is for the growing and protection of young 
plants after they have been started in hot- 
beds or forcing houses, or for the growing 
of plants in late spring after danger of severe 
weather has passed. 

Coldpits. — These are deep pits chiefly used 
for the storing of bulbs and semi-hardy 
plants during the winter. They are usually 
provided with sash roofs the same as hot- 
beds and coldframes, so that light may be ad- 
mitted when desired. 

Forcing Houses. — These are greenhouses 
used for growing or "forcing" plants at other 
times than at their natural seasons. Prac- 
tically all houses used by commercial florists 
and vegetable growers are forcing houses. 
Conservatories. — In this class of green- 
houses, plants are kept mostly for display. 
Often it is not desired that the plants so kept 


shall grow rapidly, but that they shall merely 
live. Often also they house for the most 
part such semi-hardy evergreen and other 
ornamental plants as may be grown outside 
during the summer. Such houses are com- 
mon in parks and private estates. They are 
usually ornamental in character, often with 
curved roofs, and present a lively contrast to 
the severe simplicity of the commercial forc- 
ing houses. 

Propagating Houses. — ^These houses are 
devoted principall)^ to the propagation or 
starting of plants, especially those grown 
from cuttings. As cuttings require little 
direct sunlight, these houses are often erected 
on the shady (north) side of other green- 
houses or in out-of-the-way places. They 
should be equipped with benches, underneath 
which the heating pipes should be placed to 
furnish "bottom heat.'' 

The term hothouse, as commonly used, is 
a general term synonymous with greenhouse, 
and may be applied to any of the above 

The term stovehouse is an old one, origin- 
ally applied to any greenhouse used for tropi- 


cal plants and thus of necessity kept at a high 
temperature. The use of this term is more 
common in England than in this country. 

A RANGE of greenhouses implies several 
houses more or less closely connected and 
under one management. The individual 
houses may be of any one of the classes men- 
tioned above or a combination of two or more 
classes. Such houses are often spoken of as 


A range of forcing houses is sometimes 
spoken of as a battery, and a range of sash- 
beds as a nest. 

It is said that the Romans, even before the 
time of Christ, possessed some knowledge of 
the forcing of fruits and vegetables, and util- 
ized for this purpose pits covered with slabs 
of a transparent mineral. Heat was supplied 
by fermenting manure, and occasionally by 
furnaces of masonry in which a slow fire of 
wood or dried manure was kept burning. 
How successful they were we do not know; 
but it seems certain that if any degree of 
perfection was obtained, it was because of 
the skill of the gardener rather than because 
of any special merit of the forcing pits. 


Forcing houses seem to have had their 
origin in an attempt to grow in the northern 
countries of Europe fruits such as the orange 
and grape, which were grown to such perfec- 
tion in the countries to the south. Thus in 
England the grape vine is hardy, but the 
summers are too cool and the seasons too 
short to ripen the fruit to perfection. This 
led to the training of the vines on the south 
side of buildings and walls that they might 
receive more fully the light and heat of the 
sun. Later there was conceived the possibil- 
ity of still further protecting them by the use 
of glass sash leaned against the wall. From 
this it was an easy step to the building of 
a rather permanent framework close to the 
walls, on which glass sash were placed when 
required, forming a closed house. Sometimes 
the walls were made hollow and slow fires 
built within them to give additional heat. 
Finally the idea of heating the air instead of 
the walls on which the vines were trained 
resulted in the building of brick and stone 
stoves or fireplaces within the glass enclos- 
ures. These houses were never intended for 
winter use, but simply to make the summer 
and fall conditions similar to those farther 


The attempt to grow the orange in these 
northern cHmates presented a different prob- 
lem because the trees had to be protected 
during the winter. This resulted in the build- 
ing of framework structures which were 
covered during the winter with wooden shut- 
ters and heated by means of a stone fireplace. 
There was little or no glass used, but the 
shutters were removed during the summer, 
leaving nothing but the framework to ob- 
struct the light and heat of the sun. A house 
of this description, built early in the 17th 
century by one Solomon de Gaus at Heidel- 
berg, Germany, is said to have been 32 feet 
wide and some 400 feet long, and to have 
sheltered 400 orange trees. 

The next decisive step in the evolution of 
the modern greenhouse seems to have been a 
combination of the two preceding types, de- 
signed for the growing of plants during the 
winter. They were permanent buildings 
having opaque roofs and high side walls, 
resembling dwelling houses, except that they 
were well supplied with side windows. 

At this time it was thought necessary to 
have opaque roofs to prevent freezing, and it 
became common to have a second story, 
which was used as a dwelling by the garden- 


er, in order to prevent the heat from escaping 
or the frost from "entering" through the 
roof. It was not until the early part of the 
1 8th century that glass roofs were found to 
be practicable, and they were even then slow 
in coming into use. 

The first greenhouses in this country sug- 
gestive of the modern forcing house came in- 
to existence toward the close of the i8th cen- 
tury. For the most part they were narrow 
houses of the shed-roof type, having a solid 
wall to the north and a glass roof sloping to. 
the south. They were warmed by flues, 
usually of brick, passing through the entire 
length of the house, and connected with a 
brick fireplace at one end and a chimney at 
the other. Following this, there came in 
rapid succession, improvements in form and 
methods of construction and especially in 
heating, both steam and hot water being 
used early in the 19th century. 

The real progress in greenhouse construc- 
tion in this country came with the industrial 
development of the country after the Civil 
War. The United States census reports show 
that there was but one commercial green- 
house prior to 1800; only three prior to 1820, 


and only 178 in i860. It was not until 1890 
that greenhouses had assumed sufficient im- 
portance to secure a place in the census re- 
ports. At that time there were 4,659 estab- 
lishments covering 38,823,247 square feet, 
valued at $38,355,722. 

The following table shows the total num- 
ber of square feet under glass in the United 
States and ten principal states, as shown in 
the census reports for 1910, 1900 and 1890. 
The rank of the states has changed material- 
ly during the past 30 years. 


1910 1900 1890 

Tot. Glass Grcenh*ses Tot. Glass Greenh'ses* Tot. Glass 

sq. ft 

sq. ft. 

sq. ft. 

sq. ft. ^ 

sq. ft. 













N. Y. 












N. J. 















































As stated in the preceding chapter, hot- 
beds are low structures almost wholly under- 

Fig. 1. — Hotbed in operation 

ground, but having a glass roof made up of 
sash. They are usually heated by ferment- 
ing horse manure placed in the bottom, but 
may be heated by brick or tile flues, or by 
steam or hot water. Their chief commercial 
use in for the starting of early vegetable and 
flowering plants. In the home garden they 
may be used for growing to maturity in early 
spring or late autumn, such semi-hardy and 



quick maturing vegetables as radishes and 
lettuce, and thus extend the season for sev- 
eral weeks or even months. They may also 
be used for starting and protecting early in 
the season, other slower growing crops such 
as melons, which are not transplanted but are 
allowed to mature in the beds. A gain of 
several weeks may thus be secured in the 
time of ripening. Well constructed and pro- 
tected hotbeds will withstand a temperature 
as low as zero if it is of short duration. 

Location. — The location for the hotbed 
should be (i) relatively high; (2) well drain- 
ed; (3) exposed to the sun throughout the 
day; (4) protected from north and north- 
west winds; and (5) either comparatively 
level, or sloping toward the south or south- 
west. For convenience it should be near 
some building which may be used as a work- 
room, and should be close to a supply of 
water. The south side of a building is often 
an ideal location, although there is some dan- 
ger, if the building be a light colored one, 
that the hotbed may become overheated. 

Sash. — Standard hotbed sash are 3x6 
feet, and from 1% to 1% inches thick, the 
latter being more durable but heavier to 



handle. Since they are subjected to especial- 
ly rough usage, they must be well construct- 
ed of good material, and must be kept well 
painted. Well constructed sash may be se- 
cured from any reliable dealer in greenhouse 

Fig. 2.— Standard Hotbed Sash 

A, three run sash; B, four run sash; C; Horned sash; 

X, iron rod to keep sash from spreading 

material. They may be of either cypress 
or cedar and have mortise and tenon joints, 
though the tenons should not extend quite 
through the bars, or they will be more likely 
to absorb moisture and thus decay rapidly. 
All joints should be painted with thick lead 
paint and should be put together while the 
paint is green. Sash with a light iron rod or 
bar across the middle, connecting the side 


bars, will usually prove to be more durable, 
as the rod prevents the sides from spreading. 

Most hotbed sash consist of three rows of 
glass so laid that the water will flow length- 
wise of the sash. For this purpose i8 panes 
of lo X 1 2-inch glass are required. Sash hav- 
ing four rows of glass are not uncommon, 
but the extra bar and laps obstruct so much 
light that they are less satisfactory, and they 
are rapidly going out of use. They require 
28 panes of 8 x lo-inch glass. Sash may be 
purchased either glazed or unglazed. When 
time is plentiful and the workman is handy 
with tools, they may be glazed at home at a 
considerable saving in cost. 

Well made sash may be had, unglazed and 
unpainted, at from $1 to $1.25 each. The 
same sash glazed and painted cost from $3 to 
$3.50 at the factory. The price of glass varies 
greatly from year to year, but on the average 
will cost from 75 cents to $1 per sash. 
Roughly speaking, the sash, putty and paint 
will cost about $2.25, leaving from 75 cents 
to $1.25 for the labor of glazing and painting. 
Sash of varying sizes are sometimes seen, but 
their use is not advised. It is seldom possible 
to replace them as cheaply as when standard 
size sash are used. 


When sash are glazed at home they should 
first be primed with a coat of lead paint. On 
looking them over it will be observed that 
one of the end bars is not so thick as the 
other, the upper surface being in line with 
the bottoms of the grooves or channels made 
to receive the glass. This is the lower end of 
the sash and should always be placed toward 
the south. The glazing also begins at this 
end. In glazing, the first pane is laid flat, the 
bottom of the second lapped over the top of 
the first and so on, small brads or glazing 
points being placed at the lower end of each 
pane and along the sides to hold them in 
place. Since the lap obstructs the light it 
should be as narrow as possible, an eighth 
of an inch being as wide as necessary. In 
order to obviate the necessity of cutting the 
last glass to keep the laps even, it is well to 
lay all the panes for one row on loosely, and 
to space them before fastening any. They 
should then be puttied the same as ordinary 
windows, and thoroughly painted. 

A more satisfactory way of setting the 
glass is to bed them in putty as described in 
Chapter VII, but this method is rarely used 
with hotbed sash. Sometimes the glass are 
butted ; that is, they are laid flat, end to end. 


instead of lapped. This is rarely satisfactory 
for hotbed sash; because (i) the panes are 
often not squarely cut and do not fit well, and 
(2) the sash have so little pitch or slant when 
in use that water is apt to run through be- 
tween the panes. 

Some makers offer a form of sash known 
as "horned sash/' in which the side bars ex- 
tend two or three inches beyond the end bars. 
These extensions make convenient handles 
for carrying, and it is claimed that a better 
joint can be made than when they are cut off 

flush with the end bars. 

Double-glass Sash, as the name implies, 

are constructed with two layers of glass with 
an air space of about a half-inch between. 
They have certain advantages over single- 
glass sash which may be stated as follows: 
(i) They give greater protection; (2) they 
reduce labor, as it is not necessary to use 

Fig. 3.— Double Glass Sash 


mats as late in the season; (3) in moderate 
climates no mats or supplementary protec- 
tion is needed; (4) the plants receive sun- 
light during the entire day when mats are 
not used, whereas, with single glass sash, 
the mats have to be left on until the sun 
is well up and then have to be replaced be- 
fore sundown. 

On the other hand, they have several dis- 
advantages: (i) The first cost is often as 
much as 50 per cent, greater; (2) they are 
heavier to handle; (3) they reduce the 
amount of light, especially if the glass be- 
comes loosened so that dust accumulates 
between the layers ; and (4) some users com- 
plain that they are short-lived because moist- 
ure collects between the layers and promotes 
rapid decay. 

The most enthusiastic supporters of these 
sash are those who live in climates where 
this type of sash never need supplementary 
protection, but where it is not safe to leave 
single-light sash unprotected. It is but fair 
to state, however, that their use is rapidly in- 
creasing, even in the north. 

Temporary Sash, made of oiled paper or 
treated cloth, are sometimes used for special 


purposes and give more or less satisfactory 
results. Directions for making will be found 
in Chapter VII. 

The Pit. — ^As most hotbeds are heated by 
fermenting manure, a necessary part is a pit 
of some depth in which it may be placed. 
This pit may be lined with boards, plank, 
brick, stone or concrete, the latter being the 
most satisfactory. Cypress, cedar, chestnut 
and black locust are the most durable, moder- 
ate price woods for this purpose. For data 
on concrete construction see Chapter XV. 

The depth of the pit is determined by: (i) 
The severity of the climate and (2) the kind 
of plants to be grown. As more heat is pro- 
duced for a longer time from a deep pit of 
manure than from a shallow one, it is evident 
that in cold climates and for plants requir- 
ing considerable heat, such as tomatoes and 
peppers, the pit must be deeper than in 
warmer climates, or for plants like cabbage 
or cauliflower which may be grown at lower 
temperatures. For starting early vegetable 
plants in late February or early March in 
the north, 24 inches of manure will be re- 
quired, whereas in milder climates, or later 
in the season, 12 to 18 inches will be suffi- 


cient. The manure will continue to give off 
heat for three to six weeks. 

The dimensions are determined by the 
sash. Since sash are 6 feet long and are con- 
structed to slope lengthwise rather than 
crosswise, the width of the pit north and 
south should be a trifle less than 6 feet over 
all. The length is determined by the num- 
ber of sash desired. Since they are 3 feet 
wide, it should be some multiple of three. 
For example : A two-sash bed would be 6 x 6 
feet, a three-sash bed 6x9 feet, etc. It is 
essential that the pit be well drained either 
naturally or artificially. If it is to be used in 
early spring, it is made the previous fall, 
filled with straw or manure and covered with 
boards to keep out rain and snow. When 
the bed is to be made this material is re- 
moved, leaving an unfrozen pit in which 
the new manure will heat more evenly and 
be more efficient. 

The upper or north side of a permanent 
hotbed is preferably 6 or 8 inches higher 
than the south side to give the proper 
slant to the sash. The north side may be 
about 15 inches and the south side about 9 
inches above the surface of the soil. The 
sides are connected with crossbars placed 



Fig. 4. — Plan for permanent hotbed 

even with the top, 3 feet apart, to serve as 
rests for the sash and to keep the frames 
from spreading. The sides and ends of the 
frame are well banked with fresh manure to 
conserve the heat. If the plants are to 

Fig. 5. — Permanent hotbed of concrete with cast-iron sills 

be grown in flats instead of directly in the 
soil, 2 inches of soil over the manure will be 
sufficient. If the plants are to be grown in 
the soil it should be 4 or 5 inches deep. 



Temporary hotbeds are sometimes made 
by piling the manure on the surface of the 
ground and placing a shallow frame on top. 

Fig. 6. — Plan for temporary hotbed 

This form is wasteful of manure, and the 
settling of the pile is likely to warp the frame 
so that the sash will not fit tightly. It is 
most often used when a hotbed is needed and 
a pit has not been dug the previous fall. 

Another method is to dig a pit somewhat 
larger than the frame. This is filled with 
manure to a little above the ground level. 


Fig. 7. — ^Type of hotbed used when a large amount of heat 
is required for a long time 



On top of this is placed a frame. The ad- 
vantage of this form of bed is that the frame 
settles with the manure, thus keeping the 
plants always the same distance from the 
glass. They are also warmer on account 
of the greater quantity of manure used. 

Manure for Heating. — Horse manure is al- 
most universally used in hotbeds, the pro- 

Fig. 8. — Usual type of concrete hotbed 
portion being about two parts solid excre- 
ment to one part straw or leaves. Manure 
which contains shavings is not satisfactory. 
Preparation is made lo or 12 days before the 
beds are wanted. The manure must be fresh- 
ly made and if not moist is dampened, prefer- 
ably with warm, though not hot water. 
More than enough manure to fill the pit is 
provided, for it will shrink somewhat in vol- 


ume, and some will be needed to bank the 
sides and ends. It is placed in layers in a 
pile 4 or 5 feet wide, about 4 feet high and 
as long as necessary to contain the required 
amount, each layer being lightly tramped as 
placed. This is done under cover if possible. 
After two or three days, or as soon as the 
pile begins to steam, it is re-piled, the outside 
of the first pile being placed into the center 
of the second to encourage even heating 
throughout. The manure is moistened with 
warm water if it has become dry. If prop- 
erly made a vigorous fermentation will have 
set in after two or three days and it is then 
ready to be placed in the bed. If not 
thoroughly warmed through in three or four 
days after the second handling, it is re-piled 
again every few days until fermentation is 
established. Poor heating qualities may be 
the result of: (i) Manure from poorly-fed 
horses; (2) cold weather; (3) too wet or too 
dry manure; (4) too much litter in the man- 
ure and (5) shavings or swamp hay used as 
litter instead of straw or leaves. 

If a steady heat for several weeks is re- 
quired, the manure is placed in the pit in thin 
layers and trampled quite solidly, especially 



along the sides and in the corners, keeping it 
as level as possible. Unless the hotbed is 
made so that the frame settles with the 
manure it must be filled to within 2 or 3 
inches of the top of the south side of the 
frame to provide for settling. If it is proper- 
ly made, the temperature will soon rise to 
120 degrees or more, but will gradually fall, 
and when it reaches 90 degrees the seeds 
may safely be sown. The temperature may 
be determined by plunging a reliable ther- 
mometer through the soil into the manure. 
When a hotbed is arranged to be heated 
by flues, drain or sewer tile is used, and the 
flues are connected with a fireplace at one end 

Fig. 9. — Hotbed arranged for heating by flues 

of the bed and a chimney at the other, so 
that the smoke and heat from the fire travel 
the whole length of the bed. Hot water or 


steam pipes may be run through these flues 
if desired, or they may be placed along the 
sides of the frame above the soil. 
The forcing house, because of its conveni- 
ence, possibility of heat regulation and com- 
parative cheapness of operation is rapidly 
taking the place of the hotbed in a commer- 
cial way in the starting of early plants, but 
it is promoting the use of coldframes. These 
structures rarely receive artificial heat and 

Fig. 10. — A good type of coldframe with angle iron 
corners, A 

are used largely for the purpose' of growing 
and protecting plants during mid or late 
spring, after they have been started in the 
hotbed or forcing house and until they are 
ready to plant in the open. They are, . in 
reality, simply hotbeds without artificial 
heat. When banked with manure and pro- 
tected with mats, these frames will protect 
tender plants at temperatures of 15 or 20 de- 
grees below freezings if of short duration. 




The best frames are made of cypress and 
are joined at the corners by means of angle 
irons and bolts so that they may be easily 
taken apart for storage. 

Fig. 11. — Coldframe with sash removed. The sash rest on 
the crosspieces, X. 

When large numbers of frames are used in 
relatively mild weather, they may be very 
cheaply constructed by placing two planks 
parallel to each other and 6 feet apart. The 
plank on the north side is 12 inches wide 
and the one on the south side 6 inches wide. 
When the plants are removed the planks may 
be taken up and stored, or allowed to re- 
main, and crops may be planted between 

In mild climates, coldframes may be util- 
ized for starting early plants before 
danger from frost is over, although it is often 



advisable to equip them with steam or hot 
water pipes, so that they may be heated in 
case of emergency. In the north, cold- 
frames are used for wintering violets, pansies 
and other semi-hardy plants; and farther 
south, for wintering cabbage, cauliflower and 
other plants which are started in the fall. 

Fig 12. — A cold or storage-pit with shelf for growing 


In almost every florist's or vegetable grow- 
er's establishment there is need for an out- 
of-the-way frost-proof storage, to which light 
may be admitted on occasion. Such a stor- 


age may be easily constructed by excavating 
a pit similar to a hotbed pit, but deeper, 
so that the bottom will be well below the 
frost line. This must be well drained and 
lined with a brick or concrete wall, which 
should extend a few inches above the natural 
ground level to prevent water running in at 
the top, but is banked at the top with soil or 
manure. The pit may then be covered with 
sash and protected with mats and shutters 
described in a succeeding paragraph. 

In cold climates the pit is at least 5 feet 
deep. In very severe climates a mulch of 
manure 6 inches deep placed for a distance 
of 4 or 5 feet around the pit before the ground 
freezes, will effectually protect it. As the 
normal winter temperature of the soil be- 
low the frost line is considerably above freez- 
ing, coldpits furnish excellent storage for 
gladiola, dahlia and similar plants, and also 
for bulbs for winter forcing. A row of stor- 
age pits and coldframes along the south side 
of a greenhouse is of great convenience. 
The house must be provided with a gutter, or 
the frames set a foot or more away from the 
side of the house to g^uard against breakage 



by snow or ice falling from the roof. A pit 
may be attached to the south side of a dwell- 
ing and connected with the basement. When 
the house is heated by a furnace this may be 
easily heated with little expense, and be used 
for growing vegetables or flowers through- 
out the winter. 




Forcing boxes or plant forcers are small 

coldframes with a single pane of glass, 

which are used to place over individual plants 

started early in the spring. They are used 

Fig. 14. — Types of forcing boxes or plant forcers 

for protecting tomatoes, eggplants, melons 
and other heat-loving plants, and are re- 
moved as soon as continuous hot weather 
arrives. They are used also for forcing rhu- 
barb, asparagus and other vegetables in early 
spring, and for perennial flowering plants. 

Fig. 15. — Forcing boxes in use on a commercial scale 




Sometimes hotbeds and coldframes are 

made of two rows of sash set so as to form 

a gable roof. They have few advantages 

and many disadvantages when compared 


Fig. 16. — Gable roof sash-bed heated by manure 

with those of the ordinary type. A few 
years ago it was quite common to find sash- 
beds of this kind with a sunken walk under 
the ridge in which the workman could stand, 
the heat being supplied by decaying manure 
the same as in an ordinary hotbed. Such 
beds are convenient to operate in planting, 
watering and cultivating, especially in cold 
weather. They are not a profitable venture 
as a rule, as heat can be supplied more cheap- 
ly from coal than from manure. When an 
investment has been made in a house of this 


type it will be found to be economy to equip 
ii; with an inexpensive hot water system. 


Hotbeds and coldframes, when used in 

climates or seasons in which the temperature 

is likely to fall much below freezing, must be 

provided with supplementary coveringrs. 

Fig, 17. — Rye straw marts r lulled fur slorag*; 

This is especially true when single-light sash 
are used. 

Rye Straw Mats, are extensively used for 
this purpose. They were formerly made by 
hand' but are now made by machinery and 
are fairly reasonable in price. Each mat is 


designed to cover two sash and should be 
6x7 feet to allow for turning over the ends 
of the sash to keep out the wind. An ob- 
jection to straw mats is their weight, especi- 
ally when wet, and also the fact that mice are 
likely to work in them while they are stored 
during the summer. With careful handling 
they will last three or four years. 

Fig. 18.— Hot-bed covered with (C) double glass sash; 

(B) sash and straw mat; (A) sash, straw mat and 


Burlap and Canvas Mats, which are pad- 
ded with waste cotton and quilted, are easier 
to handle than straw mats and are somewhat 
more durable. Though usually thinner than 
straw mats, they give practically as good 
protection. They have the added advantage 
of requiring less storage space, and are some- 


times treated with tar or other material of- 
fensive to mice. 

Waterproof Mats, made of heavj- canvas, 
or sometimes of oiled or rubberized fabric, 
seem to have but little advantage over com- 
mon mats, except on coldpits, when they are 
to be used during the entire winter. They 
are relatively expensive. 

Wooden Shutters, 3x6 feet in size, made 
of half-inch lumber, are occasionally used to 
place over the mats. Their chief value is in 
protecting hotbeds when made very early in 
the season, and for coldpits. 

Care of Sash-bed Materials. — ^As hot- 
beds, coldframes and the like, are used for on- 
ly a few months during the year, they are 
likely to be neglected and thus deteriorate 
rapidly. When many are used, their proper 
care may spell the difference between finan- 
cial success and failure. 

If movable frames are used, they should 
be taken down and stored as soon as the 
plants are out. If they are so constructed 
that they do not come apart, easily, they 
may be piled one above the other, cleaned and 


Sash should be cleaned and stacked under 
cover. Rainy days may be utilized in paint- 
ing them and re-glazing where necessary. It 
is economy to re-paint sash every season. 

Mats must be handled carefully and dried 
as soon as possible after they become wet by 
hanging them on a line or fence. They must 
be thoroughly dry when stored for the sum- 
mer and be kept where mice cannot get to 



Location. — Having determined upon the 
geographical location, proximity to market 
and fuel supply and the investment in land 
which the business may be expected to war- 
rant, all of which are without the scope of 
this discussion, the points next ,to be con- 
sidered in the location of a greenhouse are as 
follows: (i) It should be such that the sun- 
light will not be obstructed at any time dur- 
ing the day. The probability of high build- 
ings being erected in the immediate vicinity 
should be taken into account. (2) It should 
be well drained either naturally or artificially 
and be absolutely free of danger from floods. 
(3) It should not be exposed to cold, bleak 
winds, as they will quickly make their pres- 
ence known in excessive fuel bills. A wind 
break of evergreen or other trees will be 
found very effective in protecting from winds 
but it will be several years before the trees 
will be large enough to be of much benefit. 
^ 35 


(4) It should be comparatively level, or gent- 
ly sloping toward the south or southeast. 
Hillsides, if necessary, may be utilized by 
building houses of special design to be de- 
scribed later. (5) An unfailing supply of 
water at a reasonable cost should be assured. 
(6) If the houses are to be erected in connec- 
tion with other buildings, they should be on 
the south side if possible. For most plants 
the advantage of direct sunlight during the 
whole day cannot be over-estimated. (7) 
The possibility of enlarging the range by the 
addition of more houses should not be over- 

Arrangement. — The arrangement will de- 
pend to some extent on the size of the range 
and the purpose for which it is to be used. 
If for private use only, convenience may 
often be sacrificed for appearance ; but for the 
commercial house the first thought in ar- 
rangement is for economy in operation. 

For a commercial house the following 
points in arrangement should be considered: 
(i) The direction in which the houses are to 
run. This will be fully discussed in Chapter 
IV. (2) The distance between the houses. 
This will depend on the size and height of the 





houses and on the value of the land. Little 
advantage, except in case of heavy snowfall, 
will be gained over the ridge-and-furrow sys- 
tem (see Chapter IV) by separating the in- 
dividual houses by less than lo or 12 feet. A 
fair though not absolute rule is to space the 


u 1 

OrcAiJs j Tiosts 


Fig. 20. — Ground plan of range shown in Fig. 19 
-Boiler room is in basement 

houses at a distance equal to two-thirds their 
height. (3) The workroom should be con- 
venient to all houses of the range, yet shade 
them as little as possible. (4) Other things 
being equal, the boiler room should be at the 
lowest part of the range in order to secure 
good circulation. When the houses are long 
it is usually best to have it near the center, 
and to insure circulation by deepening the 





boiler pit, or in large establishments by the 
use of pumps or steam traps which will be 
discussed in the chapters on heating. 

Size of House. — There is no authentic data 
on the comparative efficiency of small and 
large houses. The large houses are relative- 
ly lighter, but there are other considerations. 

S£ftVK£ BiaUUMG 






Fig. 22. — Ground plan of range shown in Fig. 21 

As a rule the eastern growers favor separate 
large, high and wide houses while those of 
the Middle West prefer lower and narrower 
connected houses. The present tendency is 
to build larger houses than formerly. Of 
i6o florists and vegetable growers whom the 
author has consulted, 148 or 88 per cent, ex- 
pressed themselves in favor of houses rang- 
ing from 24 to 40 feet in width. These are 
undoubtedly the most popular widths at the 
present time, the length varying from 100 





to 500 feet or more. A discussion of the ad- 
vantages of high, wide, single houses and of 
low, narrow, connected houses is given in 
Chapter IV. 

Pitch of Roof. — The pitch of a roof means 
the degree of slant or the angle of divergence 
from the horizontal. The glass of the roof 
not only allows the light, heat and chemical 

Fig. 24. — The pitch of the roof is measured at A 

rays to pass through it, but it also acts to 
some extent as a mirror, thus reflecting a 
part of the rays. The amount lost by re- 
flection is proportional to the angle of in- 
cidence. Thus, if the sun's rays fall upon 
the roof at right angles, little or none is lost 
by reflection; but when they fall at a less 





Fig. 26, — Diagram showing how heat and light are lost 
by reflection 

angle, the amount reflected increases as the 
angle of incidence increases. The amount of 
the sun's energy lost by reflection when the 
rays strike the roof at various angles is 
shown in the following table. 

Table showing per cent, of sun's energy lost when the 
rays strike the glass at different angles 

Angle of ray Loss by reflection 

60 degrees 2.7 per cent. 



It is apparent that the maximum amount 
of the sun's energy may be secured by a roof 
presenting to its rays an angle of 90 degrees. 
It is especially important that the energy 


of the sun be conserved during the short days 
of winter. At its lowest period the sun rises, 
in the latitude of New York, scarcely more 
than 25 degrees above the horizon at noon. 
In order for the roof to present an angle of 
90 degrees to the sun's rays at this season, 
it would need to have a pitch of 65 degrees. 

Fig. 26a. — Diagram showing pitch of roof necessary to 
present an angle of 90 degrees to the sun's rays in winter 

Such a roof would be (i) very expensive to 
build and maintain, (2) would present too 
large an amount of radiating surface for the 
space covered and (3) would be too high to 
be practical in houses more than 10 or 15 
feet wide. 

If, however, we reduce the pitch to 35 de- 
grees, the sun's rays will strike the roof at 
an angle of about 55 degrees which, by refer- 
ence to the table, will be seen to incur a loss 


by reflection of between 2 and 3 per cent, on- 
ly. Roofs of this pitch are not difficult to 
build, and do not present so large a radi- 
ating surface for the area covered as do roofs 
having a pitch of 65 degrees. Roofs having 
a pitch of less than 26 degrees are seldom 
satisfactory because the snow does not clear 
from them well and they are likely to leak. 
The water of condensation which forms on 
the inside of the roof is also likely to drip up- 
on the plants when the pitch is less than 
about 26 degrees. When the pitch is greater, 
the water will usually follow down the glass 
to the edge of the house. In even-span houses 
(see Chapter IV) the pitch of the roof varies 
from 26 to 35 degrees, 26 and 32 being the 
most popular. In some specially constructed 
houses it is as great as 45 degrees. Most 
builders equip houses up to 25 feet in width 
with roofs having a pitch of 32 degrees, and 
above 25 feet with roofs having a pitch of 26 

Measuring the Pitch. — The degree of pitch 
of any even-span roof may be determined tri- 
gonometrically when the width of the house 
and the height of the ridge, is known or can 
be measured. If the house illustrated in 


Fig. 24 is 20 feet wide and the ridge is 7 feet 
above the eaves, the value of the angle, 
known as A, may be found by the following 
formula: Tang. A=^ equals Tang. A-l 
equals Tang. A=.700 or A=35 degrees. 

Should the house be of uneven span it is 
only necessary to measure the distance 
corresponding to a (Fig. 24) and apply 
the same formula. When this is not con- 
venient, a plumb bob may be dropped from 
any part of the roof, as at c, and the distance 
measured from the roof to the point c^, where 
it cuts a horizontal line or straight edge from 
the point where the roof joins the wall. This 
distance may be substituted for b in the 
formula, and the distance from c^ to the in- 
tersection of the roof and wall may be sub- 
stituted for a. To avoid error the triangle 
thus formed should be as large as possible 
afnd care taken to see that the lines are per- 
fectly viertical or horizontal, as the case may 
be. By referring to the following table the 
angles in degrees and minutes formed by 
roofs on houses of various widths and heights 
of ridge may be quickly found. The figures 
in the left-hand column correspond to half 
the width of even-span houses or to the dis- 
tance represented by a in the above formula. 



Table showing angle formed by roofs on houses of 
different widths and heights of ridge 

One half 

Height of ridge in feet 









in feet 

O ' 

O ' 

O ' 

O ' 

O ' 

O ' 

O ' 


32 21 



49 24 

• • • ■ 

• • • • 







• • • • 


26 33 


36 52 





23 57 

29 3 

33 5 

37 52 





30 58 





24 26 

28 36 


36 2 




22 57 



33 41 

36 52 

39 41 






34 42 




23 12 




35 34 


. . . . 

. • * • 


28 4 


33 40 





26 32 

It is perhaps more often desired to find the 
length of rafter necessary to form a roof of 
given pitch on a house of given width, than to 
determine the pitch of a house already 
erected. This may also be solved trigono- 
metrically. For example: Suppose it is de- 
sired to know the length of rafter necessary 
to form a roof with a pitch of 35 degrees on a 
house 20 feet wide. If the roof is to be of 
even span, as shown in Fig. 24, we will have 
a right angle triangle, A B D, the base of 
which is known to be half the width of the 
house, or 10 feet. If the angle A is to be 35 
degrees then: Cosine A=^ equals .81915= j. 
Transposing, X=--^or X=i2.2 feet. 


This formula is also applicable to an un- 
even span roof provided the distance from the 
point directly underneath the ridge to either 
side of the house is known. For example : In 
a 20-foot three-quarter span house, the base 
corresponding to a of the triangle A B D in 
Fig. 24 is either two-thirds or one-third of 
20 feet, according to which side of the roof 
we wish to measure. 

In the following table will be found the 
lengths of rafters required to form roofs of 
various angles on houses of different widths. 
The figures in the left-hand column corre- 
spond to half the width of an even-span house 
or the horizontal distance from the eaves to 
a point directly underneath, where it is de- 
sired to place the ridge. 

Table giving length of rafters necessary to form roofs of 
various angles on houses of different widths 

One half 


I in degrees 









of house 

in feet 





































































Architecturally, the different forms of 
greenhouses are named and recognized main- 
ly by the style of roof. 

Lean-to or Shed-roof Houses. — These are 
the simplest forms of greenhouses; likewise 
the least expensive and least satisfactory. 
There is little excuse for building separate 
houses of this type, but they may be made to 
serve a useful purpose when erected against 
the side of a building or against a steep side 
hill. They usually extend east and west, 
with the high wall to the north and the roof 
sloping toward the south. For commercial 
purposes they are of little value, as they ad- 
mit light from only one side, and but little 
direct sunlight, except for a few hours in the 
middle of the day. They may be utilized for 
growing ferns and other plants requiring 
little direct sunlight, also for starting early 
plants, or as grape or peach houses, the vines 
or trees being trained against the north wall. 



Lean-to houses not only have the advant- 
age over other types in less first cost, but 
also in cost of maintenance. They have less 
glass surface in proportion to the area cov- 
ered; hence there is less breakage, and for 
the same reason they radiate less heat. For 
amateur use, especially when they can be 
erected against the south side of the dwell- 
ing, they may be built and operated at small 
cost and will afford much pleasure. 

Even-span or Span-roof Houses. — In these 
houses, as the name indicates, the sides of 
the roof are of equal length. They are 
the most popular form, fully 80 per cent, of 
all houses of recent construction being of 
this type. They are superior to the lean-to 
in that they admit light from two sides, and 
also because they may be run either north 
and south, or east and west, as may be de- 
sired. On this point, however, practical 
growers disagree, some preferring the east 
and west arrangement, others the north and 
south. Theoretically, the points in favor of 
and against each seem to about counterbal- 
ance. They are stated in the following 

The north and south arrangement permits 


direct sunlight to fall on both sides of the 
house for an approximately equal time dur- 
ing the day, thus giving all the plants in the 
house an equal chance. It also permits the 
workroom to be placed on the north end, 
where it will not shade the house. The 
principal disadvantage is that during the 
middle of the daj^, when the sun's rays are 
most potent, they strike obliquely against 
the roof an^ niuch heat and light is lost by 
reflection. Moreover, a large part is cut off 
by the sash bars and rafters. 

In the east and west arrangement, the di- 
rect sunlight enters from the south side only, 
and in the morning and afternoon strikes the 
roof obliquely. During the middle of the 
day, when it is most effective, it strikes al- 
most at right angles, although it is not even- 
ly distributed and the plants on the north 
side of the house receive much less than 
those on the south side. This would seem to 
be a serious fault, but in practice is less 
serious than in theory. Of no growers 
whom the author consulted on this point, 
38 were in favor of the north and south ar- 
rangement, 42 were in favor of the east and 
west and 30 expressed the opinion that there 
is little or no difference. 



Uneven Span Houses. — The uneven dis- 
tribution of light in even-span houses 
running east and west early led to the 
experiment of cutting off the north one- 
fourth, so as to make an uneven or three- 
quarter span house. The following advant- 
ages are claimed for these houses: (i) They 
secure a more even distribution of direct sun- 
light to all plants. (2) The north span ad- 
mits indirect light which insures better re- 
sults than may be secured from a lean-to 
house. (3) The heat is more evenly distri- 
buted than in a lean-to house. They are 
often used in growing roses and other plants 
requiring a maximum of light. The con- 
struction of uneven span houses has been 
varied from time to time, the general ten- 
dency being to lower the north wall to ap- 
proximately the height of the south wall. 
This arrangement insures even better distri- 
bution of light and does away with the neces- 
sity of elevated benches. 

Uneven span houses are sometimes used 
for growing lettuce and other vegetables di- 
rectly on the ground instead of in benches, 
especially on sloping locations. Modern 
greenhouses are so much lighter than the 
older types that the advantages of the un- 




even span house in this connection are hard- 
ly worth considering. They are much less 
commonly built than formerly. Uneven span 
houses are sometimes constructed with the 
short span to- the south with a pitch of 40 
degrees or more. This brings the roof more 
nearly at right angles to the sun's rays, but 
has little or nothing to recommend it. 

Ridge-and-Furrow Houses. — A ridge-and 
furrow house is in reality simply two or more 
houses joined together. They may be even 
span or uneven span so long as the side walls 
are of equal height. The advantages of this 
form of construction may be mentioned as 
follows: (i) They are less expensive to build 
than separate houses of similar size, on ac- 
count of the saving in side walls. (2) Not 
only is there a saving in the number of side 
walls, but the interior walls may be of cheap 
construction or may be left out entirely, the 
weight of the roof being supported by posts 
alone. (3) Considerable saving is made in la- 
bor because easy passage may be had between- 
houses. (4) They conserve ground space 
which is often a considerable item. (5) The 
houses in the center are protected from wind 
by those on either side and the radiation is 


thus reduced. (6) Because there is less ex- 
posed wall surface, and because the interior 
houses are protected, they require less fuel 
than do separate houses. 

One of the chief objections to the ridge- 
and-furrow system of construction is the dif- 

Fig. 29.^Ridge-and-furrow houses wrecked by a storm 

ficulty of removing snow from between the 
houses in regions subject to heavy snowfall. 
Other disadvantages are: (i) The center 
houses are shaded more or less, (2) side light 
and side ventilation can not be had, and (3) 
soil and other materials must be carried into 
the house from the end instead of being put in 
at side openings. The latter is a serious ob- 



jection only when the houses are long and 

The above remarks refer only to separate 
and connected houses of similar sizes. At 
the present time there is a difference of opin- 
ion as to the advantages of the single wide 
and high house over the small and lower 

Fig. 30. — Diagram showing that the same amount of 
roof is required for several small, connected houses 
as for one large house covering the same area if the 
pitch is the same. a-fb-fc-fd+e-|-f=A+B. 

houses connected in the ridge-and-furrow 
system. Contrary to the prevailing notion, 
the same amount of glass is required by each 
system if the roofs are of the same slant or 

The following advantages are claimed for 
the large, single houses: (i) They are more 
easily kept at an even temperature, (2) venti- 
lation may be secured without subjecting the 


plants to cold drafts, (3) they are lighter, (4) 
they are more easily cared for, (5) the light is 
more equally distributed over the whole 
house, (6) they quickly clear themselves of 
snow, (7) they contain a larger volume of 
air, and (8) they require fewer ventilators 
and less ventilating machinery. 

On the other hand the following disadvant- 
ages are pointed out: (i) Their great height 
makes them a target for storms which in 
winter cause a greater radiation of heat, (2) 
they are less easily re-painted and re-glazed, 
and (3) the first cost is greater. 

Notwithstanding these objections, how- 
ever, the single house of moderate size (40 to 
60 feet in width) seems destined to become 
more and more popular. 

Curved-roof Houses. — Curved or curvilin- 
ear roofs are now seldom seen, except on 
conservatories and show houses. Their chief 
use is for ornamental effect. They originated 
in an attempt to so arrange the glass as to 
more perfectly intercept the direct rays of 
the sun, but in practice they have proved lit- 
tle, if any, superior to the straight roof, and 
the expense is considerably greater. They 
have never come into general use in a com- 



mercial way. Curved-roof houses are made 
to use either curved or straight glass. 

Side-hill Houses. — Mention has already 
been made of one of the forms of this type 
of house. Sometimes a modification of the 

Fig. 31. — Diagram of a side-hill range 

ridge-and-furrow house is utilized for side 
hill construction. Side-hill houses are not 
recommended when well drained, level land 
may be secured, because of the disadvantage 
of working at diflferent levels. 

Curved-eave Houses. — The shade caused 
by eave plates and gutters, the difficulty of 
keeping them in repair and their interference 




with the clearing from the roof of ice and 
snow in winter, has led to the adoption by 
several firms, of the curved-eave construc- 
tion. For small and medium-sized houses 
the increase in light is very noticeable. In 
larger houses it is not so apparent. The ex- 
pense for glass is somewhat greater on ac- 
count of the curved panes required. 

Circular Houses. — These belong in a class 
with the round barn and octagonal house — 
excellent in theory but impractical in use. 
Their first cost and the expense in mainten- 
ance places them without the range of econ- 
omy as commercial houses. As ornamental 
houses in parks and private places, and for 
the growing of tall tropical plants they have 
their place. 


Practically all the material, whether it be 
wood or metal, which goes into the construc- 
tion of a modern greenhouse, is milled or 
shaped at the factory. It will almost never 
pay the prospective builder to attempt to 
use material made by any but specialists in 
this line of work. There are several such 
firms in this country. Greenhouse construc- 
tion, then, so far as the individual builder is 
concerned, becomes simply a matter of choos- 
ing the kind of material he desires to use; 
ordering it from a responsible manufacturer 
and assembling it or placing it in its proper 
position. Most greenhouse construction 
firms have certain standard or stock houses 
which they ship complete, even including 
nails, paint and putty if wanted, at a definite 
stated price; and they will erect them if it is 
desired. They will also design and build a 
house or range of houses to suit any given 




!• Jv — ^— 4^ -4 — ^i — J 

byo V c« !3 C 



On the other hand, there is now such a 
variety of structural material to be had that 
it is quite possible, and very often desirable, 
for the buyer to design a house according to 
his own ideas or to fit his own special needs 
or location; select and purchase the materials 
and erect it with his own help to suit his 
special requirements. 

In order to do this it is necessary to know 
the names and uses of the various members 
which go to make up the house. The prin- 
cipal ones are shown in Fig. 33 and are de- 
scribed in the following paragraphs. 

Glazing-sill or Sash-sill.— This sill is bolted 
to the top of the wall, usually by bolts set into 

Fig. 34.— Types of sills. A, B, C, and D are wood sills; 
E is cast-iron 

the concrete, heads down, when the wall is 
built. It is known as a sash-sill when the 
house is equipped with ventilating sash along 



the side walls which close down against-4t; 
or as a glazing-sill when no side ventilating 
sash are used and the glass is puttied directly 
against it. Sills are used at the ends as well 
as at the sides of the house. They are of 
various sizes and forms, and may be of either 
wood or iron. The small sills are now quite 
popular. Grooves on the under side of the 
wood sills prevent the water from running 
back between the sill and the wall which 
would thus cause decay. 

Eave Plate. — This plate rests upon the side 
posts and forms the support for the roof 
members. It may be of either wood or iron. 

Fig. 35. — Types of eave plates. A, B, C, and D are 
wood; E is a metal plate 

Gutter. — When it is desired to collect the 
water from the roof, or when houses are con- 
nected in the ridge-and-furrow system, it is 
necessary to use a gutter instead of an eave 



plate. Iron gutters are rapidly displacing 
the old-fashioned wood gutters as they last 
longer, and because they need not be so large 
and hence cast less shade. 


Fig. 36, — Types of gutters. A, and D are wood; B, and 

C are metal. C is supported by two rows of posts 

to allow for a walk directly underneath 

When gutters are used, they have a fall of 
at least 4 inches for each 100 feet in length. 
This is accomplished by gradulally shorten- 
ing the posts toward one end of the house. 
In other words, the side walls are higher on 
one end of the house than they are on the 
other. On very long houses the walls are 



Fig. Zl, — Type of gutter 

(a) used on curved- 

eave houses 

sometimes so construct- 
ed that the gutter 
slopes from the ends 
each way toward the 
center and the water 
is carried away at 
that point. Detached 
houses are less com- 
monly fitted with gut- 
ters than formerly, on 
account of their inter- 
ference with the clear- 
ing of snow. A special 
form of gutter is used 
on curved-eave houses. 

Glazing Bars. — These are bars which are 
^ spaced along the sides and ends of the house 
to which the glass is 
fastened. They are 
much the same as sash 
bars, which will be 
described later, except 
that they are usually 
somewhat smaller and 
are not provided with 
grooves to conduct 

the drip. Corner bars 

Fig. 38. — Cross section of 
corner bar 


serve the same purpose as glazing bars, ex- 
cept that they are so milled that they will 
take the glass from both the sides and the 
ends of the house. One is used at each 

Side Posts. — These posts bear the weight 
and side strain of the roof. They may be 
of wood, gaspipe, or structural iron or steel. 
Their size will depend on the height of the 
wall and the width and construction of the 
house. Wood posts 4x4 inches, 2 or 2/^- 
inch gaspipe, or >4 x 3-inch structural iron 
or steel are usually considered amply strong 
for most houses. The gaspipe and steel 
posts are usually set in concrete and mason- 
ry. It is best to set the wood posts in the 
same manner. Occasionally the structural 
steel posts are bolted to iron sills which cap • 
a concrete or masonry wall. 

Sash Bars. — The sash bars are among the 
most important of all the members which go 
to make up a greenhouse. They must be 
strong enough to carry the weight of the 
glass, yet be of such form and size as to 
cast the least possible shade. They are 
of various forms and sizes. Bars made en- 
tirely of metal are seldom satisfactory for 



the following reasons: (i) They are likely to 
expand and contract considerably with 
changes in temperature, thus loosening and 

u=y M 

Fig. 39. — Types of wood sash-bars. E, F, and H are used 
for butted glazing; G is used for double glazing 

often breaking the glass. (2) The extreme 
cold to which they are subjected on the out- 
side, as compared with the warm tempera- 
ture on the inside of the house, has a ten- 
dency to cause them to warp and thus break 
the glass or cause it to fit poorly. (3) As all 
metals are ready conductors of heat, much is 
lost by radiation when they are used. (4) In 


cold weather they become so cold as to cause 
the moisture in the air inside the house to 
condense rapidly on them, which results in a 
large amount of drip. Various types of bars 
have been invented in an attempt to over- 
come these difficulties. 

Fig. 40. — Two types of patented metal sash-bars 

Wood sash bars are not good conductors 
of heat and condense but little moisture, but 
moisture from the glass finds its way to the 
sash bars, so that they are usually made 
with a groove or furrow on each side, which 
conducts the moisture down to the eaves. 
The most common size of wood sash bars is 
iH X 2y2 inches. Larger bars are used for 
special purposes. 







--—"—— ; 



Fig. 41. — King "channel bars" 

Fig. 42. — "U-Bar" type of sash-bar 



Fig. 43.— Gable 

Drip Gutter.- 

gutter is to 
carry away the 
water formed 
b y condensa- 
tion inside the 
house, which is 
conveyed to it 
by the sash 
bars. The pipes 
leading from it 
should empty 
into a cistern 
or sewer con- 
nection inside 
the house, or be 

Gable Bars or 
Gable Rafters. — 

Gable rafters are 
used at the ends of 
the roof and are 
made so as to re- 
ceive both the glass 
of the roof and that 
of the end of the 
house. They should 
be large and strong- 
enough to give ri- 

rafter gidity to the gable. 

—The purpose of the drip 

Fig. 44. — Combination eave plate 
and gutter 


carried out below the frost line. This is neces- 
sary to prevent freezing, as the greatest drip 
is in the coldest weather. In some forms of 
construction where pipe side posts are used, 
they are utilized as conductors of the drip 
water, but the saving thus accomplished is 
usually more than counter-balanced by the 
early rusting out of the posts. Gutters are 
made of wood, zinc, tin and galvanized iron. 

Purlins. — Since sash bars must be small 
to minimize the amount of shade, it is evident 
that on wide houses they cannot carry the 
weight of tile glass without support. This is 
accomplished by means of purlins. They 
run lengthwise of the house, and are them- 
selves supported by purlin posts, by purlin 
braces, by rafters or by some form of truss 
work to be described later. 

When ordinary wood sash bars are used 
with glass i6 inches wide, the maximum dis- 
tance for safety between purlins is not more 
than 7 feet. For example: If the sash bars 
are more than 7 feet long, one purlin should 
be used. If they are more than 14 feet long, 
two purlins should be used, and so on. This 
distance decreases as the size of the glass in- 
creases since there are fewer bars to sustain 
the same weight. 



Purlins may be of wood, gaspipe or angle 
iron. Wood purlins, because of their size 
(1^x3 inches), cast so much shade that they 
are now little used. Purlins of i>4-inch gas- 
pipe are very satisfactory. They are fast- 
ened to each sash bar, and are supported by 
posts or braces every 8 feet along their 

Fig. 45. — Pipe -strap for fastening sash -bars to purlins 

length. A very satisfactory means of fast- 
ening them to the sash bars is by means of a 
U-shaped pipe-strap. This is placed under 
the purlin and fastened. to the sash bars by 
means of screws. 

Ridge. — The ridge furnishes a means of 
fastening the upper ends of the sash bars and 
also serves as a support for the ventilators. 


It IS milled from a 2 x 4, or a 2 x 6-inch tim- 
ber, the size depending on the width of the 
house. The form varies according to the 
method of attaching the ventilators. (See 
Chapter VIII). 

Ventilators. — These are fully discussed in 
Chapter VIII. 

Ventilator Header. — This is a member up- 
oa which the lower side of the ventilator 
rests, it is cut and grooved at the factory 
so as to fit over the sash bars and to receive 
the edge of the glass of the roof in its lower 

Sash Hanging Rail. — When side ventilat- 
ing sash are used a special piece is sometimes 
placed immediately under the eave plate or 
gutter, to which the sash are hinged. This is 
known as a sash hanging rail. Sometimes 
the sash are hinged directly to the plate or 

Weather Strip. — Because of their construc- 
tion and the method of hanging, the roof 
ventilating sash do not fit down tightly upon 
the sash bars but leave wedge-shaped open- 
ings. These are closed by pieces known as 
weather strips. 


Rafters. — Their use is now confined al- 
most wholly to all-metal frame houses which 
are discussed in Chapter VI. 


Three kinds of wood are now being used 
in greenhouse construction: Cypress, cedar 
and California redwood. Of these the first 
two are preferred on account of the higher 

Fig. 46. — "Pecky" cypress 

cost of redwood. There is little difference 
in the durability of cypress and cedar. If 
well framed, and if thoroughly painted when 
erected and at least once in two years there- 
after, either will last a lifetime. 

Pecky cypress is the heartwood from old 
trees. It is full of holes or "pecks" and is 
often too "shaky" for sash bars and other 
small members, but it is one of the most dur- 
able woods known. It is used chiefly for 
benches, and in other places where ordinary 
lumber decays rapidly and where great 
strength is not needed. 



The woodwork of a greenhouse always be- 
gins to decay at the joints. For this reason 
particular attention is paid to the framing. 
All joints are made to fit closely, and before 
putting together each piece should be primed 
with a thin coat of lead paint. The joints 

Fig. 47. — The concentric system of construction 

are then given a heavy coating of thick white 
lead and put together while the paint is still 

In buying greenhouse material it is al- 
ways well to buy all the woodwork from one 
firm and to give the concern a careful de- 
scription of the house, together with a draw- 
ing showing the width, height and length of 
the house, the pitch of the roof, size of glass 
to be used, etc. The firm will then send the 


woodwork (if it is so directed) cut so that 
it may be fitted together with but little 
trouble. It should be specified, however, 
that it be well seasoned and not warped. 
Warped millwork, especially sash bars and 
glazing bars, are exceedingly difficult to put 
in proper position. 

Some factories now build their eave plates 
and sash bars on the concentric principle, 
which does away with the necessity of cut- 
ting the ends of sash bars differently for 
roofs of different angles. 


The two cardinal virtues of a good green- 
house framework are these : It must be strong 
and light, and it must cast but little shade. 
The greatest advance in greenhouse con- 
struction in the last quarter of a century has 
been in the framework. The. old houses with 
their high, solid walls and heavy woodwork 
are dingy and dark, when compared with the 
modern house, 90 per cent, of which is glass, 
with little or no solid wall above ground. The 
framework of these houses casts but a frac- 
tion of the shadow produced by the old-style 
frame, yet it is so perfectly rigid against 
storms and snow that the large panes of glass 
are seldom broken or even loosened in their 

Three general classes of framework are 
used: (i) Wood frame, in which all members, 
including the posts, are of wood; (2) semi- 
iron frame, in which the posts, purlins and 
purlin posts are of pipe or structural iron, 





and (3) all-iron or all-steel frame. In wood 
and semi-iron construction, rafters are sel- 
dom used, the sash bars performing this func- 
tion as well as their own. These forms have 
the advantage of being somewhat cheaper 
than the all-metal frame construction, and 
have the additional advantage that the ma- 
terial may be cut and fitted on the job by any 
experienced workman. 

Wood frame houses cast more shade than 
semi-iron, and are less durable, especially the 
posts. Semi-iron houses are very durable, 
and for houses of medium width, are very 
satisfactory. Probably more houses of this 
type have been built during the past ten years 
than of all others, though the all-metal frame 
house is now gaining in favor. This is 
especially true in the East, where large 
houses are coming into vogue. 

The all-metal frames are cut and fitted at 
the factory and are then shipped, knocked 
down, to the place of erection. Most styles 
of all-metal frames have rafters, which are 
bolted to the side posts by means of gusset 
plates to form bents. The bents are then 
f)laced in position and secured there by stays 
and purlins. Upon this framework are then 
bolted the wood sash bars and glazing 


bars. Metal sash bars, as before mentioned, 
seldom prove satisfactory. The framework 
of such houses is practically indestructible, 
and when the woodwork decays it can be re- 
placed upon the old framework. 

Usually the weakest part of a greenhouse 
is the gable. It should be well framed and 
securely tied to the purlins and other parts 
of the framework. 


Foundations and Walls. — In the old-style 
high, solid wall greenhouse, the wall was a 
source of much perplexity, especially the 
high north wall of the uneven span house. 
In modern houses, however, the solid wall is 
seldom higher than the top of the benches, 
when benches are used, or only a few inches 
above the surface when plants are grown on 
the ground. The remaining part of the side- 
wall is constructed of posts and glass, thus 
giving more light. The chief difficulty with 
the high, solid wall was that the extremes of 
temperature between the outside and inside 
in cold weather caused them to disintegrate 
rapidly. This was particularly true with 
masonry walls. 


Modern greenhouse walls, for commercial 
houses, are almost always of concrete and, 
being low, give little trouble. Concrete 
blocks and hollow building tile are much 
used. The chief requisite. is that the founda- 
tion shall reach below the frost line. The 
common practice is to dig a trench 12 or 
15 inches wide and 3 feet deep and fill with 
coarse concrete to within a few inches of the 
surface. A form is then built of lumber to 
the height reiquired and filled with concrete. 
When the concrete has "set," the form is 
taken away and the sides of the wall plast- 
ered with a cement mortar. In wet, springy 
soil it is often desirable to lay a row of drain 
tile along the outside of the wall and nearly 
to the bottom of the trench, to carry off the 

Concrete walls are usually much more 
satisfactory than either brick or stone. They 
should be from 8 to 12 inches thick, according 
to their height and the side strain to which 
they are subjected. Usually 8 inches is suf- 
ficient. In wet soils when the boiler is placed 
below the surface, it may be necessary to 
waterproof the walls. For data on concrete 
construction see Chapter XV. 



Wood Frame Houses. — These are quite 
satisfactory when a cheap house is wanted 
for a comparatively few years. The side 
posts, which may be of cedar or cypress, and 
3x4 inches in size, are placed 8 feet apart 
in holes 3 feet deep, and extend to the height 

Fig. 49. — Plan for an all-*wood frame greenhouse 

decided upon for the side walls. They are 
then placed in alignment and the holes 
poured full of thin concrete which soon hard- 
ens. The end posts are similarly placed, ex- 
cept that they extend only to the height of 
the boarded-up portion of the wall. 


The next step is to place the center posts, 
which are usually 2 x 3 or 2* x 4 inches in 
size. The height of the ridge having 
been determined (see Chapter III) these 
posts are cut long enough to allow the 
lower end to be set in the ground about 2 
feet. They are then put in alignment and 
embedded in concrete the same as the side 
posts. The ridge is then put in place on top 
of these center posts, and the eave plate on 
top of the side posts, all joints being set in 
thick white lead paint. 

The sash bars on a house over 12 feet in 
width must be supported with purlins, but it 
is not necessary to support them with two 
extra rows of posts. A perfectly safe and 
much more convenient way is to support 
them with arms or braces from the center 
posts. This saves valuable ground space, and 
the arms serve to stiffen the center posts as 
well. The length and position of these arms 
may be determined by placing a straight edge 
from ridge to eave plate in just the position 
the sash bars will occupy, and nailing the 
arms fast, first allowing for the thick- 
ness of the purlin. A good mechanic would 
have determined this before the posts were 


set, and have nailed the arms in place before 
raising them. The amateur, however, will 
find it best to put them in place after the 
posts are up, or at least to put up a trial post 
and then make the others after it as a pattern. 

The next step is to nail on the purlin, and 
then it is ready for the sash bars, which are 
spaced carefully so that the distance from 
rabbet to rabbet is about one-eight-inch 
greater than the width of the glass. This 
can best be accomplished by using a board 
about one-eight-inch wider than the glass, 
and nailing the bars so that the rabbets fit 
snugly against it along their whole length. 
The board can then be removed and used to 
space the next, and so on. 

The side and end posts are next boarded 
up to the required height, using two layers 
of matched lumber with paper between. The 
bottom board, at least, must be of best qual- 
ity pecky cypress to guard against decay. 
Glazing bars may now be fitted along the 
sides between the eave plate and the glazing 
sill, and between the glazing sill and the 
gable rafters. • Corner bars are placed at 
each corner. 


It will also be necessary to make a frame 
for the door at one end, and to reinforce the 
gable glazing bars with 2 x 4-inch scantling. 
The house is then ready for glazing, instruc- 
tions for which will be found in Chapter VII. 

If cypress or cedar lumber is used through- 
out, and if kept carefully painted, a house 
like the above should last for fifteen or 
twenty years. The most vulnerable parts are 
the posts, especially the portion where they 
enter the cement. They should be painted 
regularly once each year at this point. While 
these houses do not admit as much light as 
either a semi-iron or an all-iron frame they 
will give excellent service. A poorly built 
all-wood frame house is a constant expense 
for maintenance. 

Semi-iron Frame Houses. — Two methods 
of framing a semi-iron frame house are 
shown in Fig. 33. The method shown on the 
left requires twice as many purlin posts as 
the one on the right. In each case gaspipe 
is used. The work of erecting diflfers but 
little from that described for wood frame 
houses, except that pipe working tools are 
required, and a little more skill is necessary. 
An endless variety of fittings may be had 



for this style of framing, which makes the 
joining of the frame work comparatively 

If it can be procured, genuine wrought- 
iron pipe is best used instead of the steel pipe 
now commonly sold. Steel pipe rusts out 

Fig. 50. — ^Two methods of framing a semi-iron house 
For others, see Fig. 33 

much more quickly. In this style of house the 
wall is usually of concrete and may be only a 
few inches above the surface of the ground, 
or any height desired. The side posts which 
are usually of 2-inch pipe are put in position 
and stayed before the concrete is poured in, 
so that when th^ wall has set they are per- 
fectly rigid. Adjustable brackets which fit 
on the top of the posts, and to which the 
eave plate or gutter is attached, make pos- 
sible the correction of trifling variations in 

Bolts are set, heads down, in the top of the 
wall while it is soft, and project upward 2 or 
3 inches. These are used for fastening down 



the sill, which is bored to fit over the posts 
and bolts and is secured with nuts. No 
posts are set in the end walls, but the bolts 
are set the same as in the side walls and are 
used for the same purpose. 
In some cases the posts are 
set in the ground and the side 
walls are constructed of two 
layers of matched lumber. 

The purlin posts and other 
supports are put in position 
much the same as in the wood 
frame house, except that in- 
stead of being embedded in 
concrete, they are sometimes 
provided with foot pieces and 
rest on small concrete piers. 
Split malleable iron castings 
may be had in almost every 
conceivable form for joining 
the frame together. These are 
fastened by bolts and set screws, so that it is 
not necessary to thread the pipe. The sash 
bars are fastened to the pipe purlins by 
means of U-shaped clips or pipe-straps, 
which are secured to the bars by means of 
screws. Purlins are usually made of one and 

Fig. 51. — Struc- 
tural steel post 
with board 


a quarter-inch pipe and should be supported 
by posts every 8 feet. Purlin posts are usual- 
ly of one and a half-inch pipe and braces of 
one and a quarter-inch pipe. 

A well-built house of this type, if well 
cared for, should last a lifetime. 

Fig. 52. — Section of truss-frame greenhouse. The frame 
is made of gaspipe 

Semi-iron frames are also made from struc- 
tural iron instead of pipe. They are just as 
satisfactory, but are not so easily worked, 
and are usually cut and fitted at the factory. 

All-metal Frame Houses. — There are three 
types of all-metal framework: (i) Those in 
which the roof is supported by interior posts, 
much the same as in the wood or semi-iron 
houses. (2) Those in which the roof is sup- 



ported by a truss work, thus doing away with 
all interior posts (sometimes known as truss- 
frame). (3) A combination of the above 
forms (known as a combination truss-frame) 
is used in houses so wide as to make the 
truss-frame impractical. This is commonly 
used in houses over 40 feet in width. 

Fig. 53. — Section of combination truss-frame green- 
house, 172 feet wide 

As has already been mentioned, all-metal 
frame houses usually have wood sash bars 
and glazing bars, but they are not considered 
as parts of the framework. In these houses 
the completed framework is entirely of metal, 
the wooden members being fastened to the 
frame with bolts or screws and serving only 
to hold the glass in place. 

In many all-metal frame houses, especially 
when the roof is supported by inside posts, it 
is common to bolt an iron or steel sill to the 
wall and then bolt the side posts to this sill. 

A method of erecting a modern combina- 
tion-truss frame house, 73 feet wide and 




nearly 30 feet high, to the ridge, is shown in 
Fig. 54. This work was done entirely by 
the owners and their ordinary help, without 
any expert superintendence and at a material 
saving in cost. 

The method was comparatively simple. 
The material was first carefully distributed 
on the site selected, and a .trench dug for 
the foundation. The gable trusses were 
then bolted together, while another gang of 
men began setting and guying the side posts. 
The trench was then filled with concrete, 
making the side posts rigid. Next the in- 
terior posts were put in place. 

The first step in putting up the rafters 
was to fasten the lower ends to the tops of the 
side posts loosely, so that they would move 
easily, and then raise the other end into place 
by means of a pair of "shears," made of two 
pieces of 2 x 4-inch scantling. When these 
had been securely bolted in place, the gable 
truss, which had been previously assembled, 
was swung into place by means of a block 
and tackle, working from a boom. All 
that rerftaing^d was to insert and tighten the 
bolts, put the purlins in place and move on 
to the next bent. The author was told by 
the owners of this house that it was erected 




with greater ease than any semi-iron house 
they had ever built. 

Fig. 56.— A method of 
erecting small all-metal 
frame houses 

Structural steel is most largely used in 
truss-frame houses though gaspipe is now 
quite popular. It is claimed for gaspipe that 
it costs less than structural steel and that it 
casts less shade. Some objection has been 
urged against houses constructed of gaspipe 
on account of a lack of rigidity, but as now 
constructed they give very satisfactory serv- 
ice. Houses of this type are regularly sup- 
plied by manufacturers up to 54 feet in width, 
without center supporting posts. It is prob- 
ably safest to have two rows of supporting 
posts in houses more than 40 feet in width. 



Greenhouse glazing is an art in itself. 
Most construction firms employ professional 
glazers. It is, however, an art that may be 
readily acquired. Many owners do their 
own glazing when occasion requires, or have 
it done by their ordinary help. The method 
of glazing greenhouse roofs is not the same 
as that used in glazing window sash. When 
glazers from glazers' shops or hardware 
stores are employed, precaution should be 
taken to see that they understand the differ- 

Glass. — The glass commonly used in 
greenhouse glazing is clear, white, sheet or 
window-glass of either A or B grade. Glass 
with a pronounced green or bluish cast is to 
be avoided, as it obstructs a large part of the 
heat, light and chemical energy of the sun's 

Clear, white window-glass ordinarily ab- 
sorbs about 30 per cent, of these rays ; green, 



from 40 to 50 per cent.; and blue, from 50 
to 80 per cent. 

Glass known as A, or first grade, is blown 
from the top of the retort and is of bet- 
ter quality than the B, or second grade, 
which may contain some foreign matter or 
settlings. Some of the less regular panes 
from the first blowing and those containing 
small air bubbles are also placed in the B 
grade. When it is essential that the great- 
est possible amount of light be had and tight 
glazing is necessary, A grade is used. 

In most commercial constructions B grade 
will give satisfactory results. Poorer grades 
are not satisfactory for greenhouse work. 
The cost of B grade is about 85 per cent, of 
the price of A grade. Both A and B grades 
may be had in two weights or thicknesses, 
known as single-thick and double-thick. 
Single-thick runs about 12 panes to the inch 
and weighs from 19 to 21 ounces per square 
foot. Double-thick runs about 8 panes to 
the inch and weighs from 26 to 29 ounces 
per square foot. Double-thick is almost 
always used when the panes are more than 
8 X 10 inches in size. It obstructs but little 
more light and is much more durable, 
especially against hail. 


The price of single-thick is from 60 to 70 
per cent, of the cost of double-thick. Amer- 
ican window-glass is the best that can be 
procured. The price varies greatly from year 
to year, probably more than does the price 
of any other standard building material. 

American-made glass is packed in boxes of 
about 50 square feet each. Foreign glass 
comes in boxes of approximately 100 square 
feet each. The number of lights per box of 
the various sizes of American-made glass is 
shown in the following table: 





per box 


per box 

7x 9 




8x10 . 









■ 60 























Plate glass is seldom used in commercial 
greenhouses, as its cost is prohibitive. It is 
but little better than A grade window-glass 
for this purpose. In conservatories where 
strength is more important than transpar- 
ency, fluted or corrugated glass, or glass in- 


to which wire netting has been blown is 
sometimes used. Ground or frosted glass is 
occasionally used in palm-houses or ferneries, 
where a soft, subdued light is desired. This 
effect is more commonly obtained by paint- 
ing or whitewashing the clear glass and vary- 
ing the thickness of the coating according to 
the season of the year. 

Size of Glass. — The size of the glass varies 
according to the purpose for which the house 
is to be used, and the taste and personal pref- 
erence of the owner. Where extreme light- 
ness is wanted, large panes are used thus 
diminishing the number of sash bars. There 
is, however, a practical limit to the size. Glass 
increases rapidly in price as the size in- 
creases, and the large panes break more 
easily. Moreover, the size of the sash bars 
must be increased to carry the extra weight, 
and every increase in their size means more 

Of 136 practical growers consulted on this 
point, 108, or. nearly 80 per cent., favored 
either 16 x 20 or 16 x 24-inch glass with the 
longer edge parallel to the sash bar. That 
is, the great majority preferred to have the 
sash bars spaced about 16 inches apart. 

GLAZING AND PM^T.WP •'-*':•: ii^l. 

About 3 per cent, favored i6 x 2oinch glass 
with the shorter edge parallel to the sash 
bars, the bars in this case being 20 inches 
apart. Glass 16 x 20 inches is undoubtedly 
the most popular size. 

Methods of Glazing. — Practically all 
methods of glazing make use of putty to seal 
the glass in place and to form an air and 
water-tight joint. An exception is made 
when some forms of metal bars are used. 
With these, felt, candle wicking or some 
similar material is usually employed, and the 
glass is pressed firmly against it and kept in 
place by bolts or clamps. Sometimes a lead 
facing is used and the glass is clamped 
against this facing. 

The great majority of houses are con- 
structed with wood sash bars or bars having 
wood cores with which putty is supposed to 
be used. With these there are two common 
methods of setting the glass. It may be 
lapped or butted. 

Lapped Glazing. — In lapped glazing the 
lowermost panes in each run are laid flat 
against the bottom of the grooves in the 
sash bar. Each succeeding pane is then laid 
so that its lower edge laps over the upper 

\m\ y\ \ : .: fcEEENHOUSES 

edge of the pane below it, in much the same 
way that shingles are lapped, except that the 
lap is much narrower. From one-eighth to 
three-eighth inches are allowed for lapping, 
the width of the lap. depending somewhat on 
the size of the glass and the rigidity of the 
house and roof. It should be as narrow as 
possible, for little light passes through the 
lapped part of the roof. 

Fig. 57. — Lapped glazing 

Butted Glazing. — In butted glazing all 
panes lie flat against the bottom of the 
grooves in the sash bars, and the lower edge 
of each glass rests directly against the up-, 
per edge of the one below. This form of 
glazing eliminates the lap, but it is more dif- 
ficult to secure a tight roof than when 
the glass is lapped. Roofs having a pitch 
of less than 30 degrees are likely to leak badly 
when the glass is butted. 

In this form of glazing the putty is some- 
times omitted, and the glass is held in place 
by wood caps which fit over the rabbets. 
When it is desired to make an especially tight 


roof, the upper and lower edges of the panes 
are sometimes dipped in a shallow tray con- 
taining thick paint. They are laid while the 
paint is soft, and in hardening this forms a 
tight, waterproof joint. Zinc glazing strips, 
bent in the form of a letter Z were at one 
time quite extensively used between the 
panes to make a tight joint. They are still 
used to some extent between the panes on 
side and end walls. 

Several advantages are claimed for butted 
glazing: (i) Less glass is likely to be broken 
by accidents, for if only one pane is hit, it 
only will be broken; while if the panes are 
lapped, the one immediately below is often 
cracked. (2) Less glass is broken by the ac- 
tion of frosts, as there are no laps in which 
moisture can collect and freeze. (3) The 
roof is lighter, as there are no laps to ob- 
struct the sunlight. 

The chief disadvantage, aside from leak- 
age, is the difficulty in repairing the roof 
when a glass is broken, for the pane must 
be cut to fit tightly. In cold, stormy 
weather, this is a slow and tedious process. 

Butted glazing is much less used than 
formerly among practical growers, which is 
proof that, in general, it is not so well suited 



Fig. 58.— Putty knife 

for glazing roofs as is 
lapped glazing. More than 
90 per cent, of the growers 
interviewed on this subject 
preferred lapped glass 
roofs. On side and end 
walls, glass is quite com- 
monly butted with good 

Putty. — Putty is a pli- 
able substance used in set- 
ting glass. The principal 
ingredients are whiting 

and linseed oil, and its chief virtues are that 

it is easily worked and applied, and that it 

does not shrink on 

drying, thus making a 

water-tight seal. For 

greenhouse use, putty 

as bought in the gen- 
eral market should be 

mixed with pure white 

lead at the rate of one 

part of lead to five of 

putty. This will stick 

to the bars and glass 

much better than will Fig. 59.-Machine for dis- 

ordinary putty. tributing putty 



Putty purchased from dealers in green- 
house supplies will not need the addition of 
lead. It should be worked as soft as it can 
be handled in order that it may be easily 
forced into all cracks and crevices. It is 
applied with a putty knife or with a putty 
machine. The putty machine distributes the 
putty rather more rapidly than can be done 
by hand, but it is necessary to use a putty 
knife in conjunction with it. 

Setting the Glass. — The basic difference 
between glazing greenhouse roofs and glaz- 
ing ordinary window-sash is in the method 
of applying the putty. In glazing window- 
sash, the putty is placed on the outside. In 
greenhouse glazing the putty is placed in the 

A. H 

Fig:. 60. — A, window glazing; B, greenhouse glazing 
The putty is shown at a and b 

grooves in the bars and the glass is forced 
into it. That which oozes up around the 
edges is scraped off and used again. By this 
method, little putty is exposed to the air, but 


the glass is sealed by a thin film underneath 
and along the sides of each pane. This 
method has been developed because experi- 
ence has shown that on roofs putty soon 
checks and crumbles away when exposed to 
the weather as in window glazing. 

When glass is lapped, the following meth- 
od is used. First, the sash bars should have 
been so placed that the space left for the glass 
is about one-eighth of an inch wider than the 
glass. This provides room for the "side 
putty." (For method of spacing see page 
87). Sash bars are usually primed when re- 
ceived from the factory. They are given an- 
other coat of paint after they are put in 
place and are then ready for glazing. 

Glazing is started at the bottom of the run. 
A line of soft putty is first placed in the rab- . 
bets and a pane of glass forced firmly into it 
until it is imbedded against the bar. A 
groove is usually provided in the plate to re- 
ceive the lower edge of this glass to prevent 
it from sliding down, but if there is no such 
groove, three or four brads or glazing points 
are driven for the lower edge to rest against. 

The excess putty is then removed and the 
next glass forced firmly into place, so that 
its lower edge laps over and rests firmly on 


the top of the first, and its upper edge rests 
on the sash bar. This is fastened at the bot- 
tom with brads or glazing points to prevent 
its sliding down. The remaining panes of 
the run may then be placed in the same man- 
ner, special care being taken to secure the 
uppermost firmly in place with glazing 
points. This is necessary because it has no 
glass above it to hold it in place, and because 
it acts somewjhat as a key to keep the others 
in position. 

It is best to finish each run from bottom 
to top before starting on a new run, in order 
that the putty may cement into a continuous 
mass. On high and wide roofs, however, it 
is sometimes advisable to glaze the lower 
half of the roof, then move the scaffolding 
and glaze the remainder. 

How to Estimate Putty. — The amount of 
putty necessary to glaze a roof may be esti- 
mated as follows: A pound of putty, when 
applied by an experienced workman, will 
reach about 15 feet along one side of a run 
of glass or about yV^ feet along both sides. 
To estimate the amount of putty, therefore, 
multiply the length of the run in feet by the 
number of runs and divide by 7/4. This will 
give the number of pounds required. The 



amount required for the sides and gable may 
be found in the same way. An inexperienced 
workman will use somewhat more than this 
amount as there will be more waste. 

In glazing by the "butted glass" method, 
putty may or may not be used. When it is 
used, the method is very similar to that de- 
scribed above, except that much 
less is required, as the panes are 
crowded down to the bottom of 
the rabbet along their whole 
length instead of only at their 
upper end. Sometimes in glazing 
by this method no putty is used 
until after the glass is laid, and 
then a small quantity of liquid 
putty is forced down along the 
sides of the glass with a putty 
Fig. 61. — bulb. Usually when the glass is 
Putty bulb butte^i^ the bars are surmounted 

by wood caps. In this system special care 
must be taken to fasten the lower pane, as 
the sliding weight of the entire run rests 
against it. 

Glazing Points. — Glazing points are used 
to hold the glass in place. They may be 
had in several forms and sizes. A good 
glazing pomt is easily driven, does not split 



the wood, offers as little obstruction as pos- 
sible to the brush in painting and does not 
rust. Small sizes suitable for glazing win- 
dow-sash in which the putty is placed on 
the outside are too small for greenhouse glaz- 
ing. Zinc points of various forms have 
been frequently used because of their free- 
dom from rust. The triangular point is prob- 
ably the most popular of the zinc points, and 

Fig. 62. — Types of glazing points 

is quite commonly used in window glazing. 
It is not well suited to greenhouse glazing 
on account of the difficulty of fastening the 
panes of glass with it so that they will not 
slide down the roof. 

Probably the most used point in green- 
house glazing is the double-pointed staple. 
This is easily driven and when galvanized is 
not subject to rust. The best form of this 
type of staple is bent to an angle in the cen- 
ter, so as to fit over and hold the lower edge 



of the pane from slipping lengthwise, as well 
as to hold it down in place. 

In lapped glazing only two double points 
are used for each pane, that is, one at each 

Fig. 63. — Glazing with double glazing points 

lower corner. The upper edge is kept in 
place by the bottom of the pane above it. Ad- 
ditional points are required for the lower- 
most and topmost panes in each run, and as 
some will be lost and destroyed, it is well to 



figure on three points for each pane. An 
average of five of the small single points will 
be required for each pane. 

Fig. 64. — Glazing with single glazing points 

Precautions. — ^AU sheet glass is slightly 
curved, a condition caused by the process of 
manufacture. When seconds or B grade 
glass is used, it will sometimes be found that 
the panes will be so much curved as to make 


it difficult to lay a tight roof. If this trouble 
is experienced, it will be of advantage to sort 
the glass and lay out each run on a smooth 
floor, placing the panes having a similar de- 
gree of curvature in the same run. By doing 
this a tighter and more satisfactory roof can 
be laid. 

Theoretically, the glass will resist more 
pressure if it is placed so that the curve will 
be up, that is, so that it will present a convex 
surface to the weather. If, on the other 
hand, it is placed so as to present a concave 
surface to the weather, the water will have 
a tendency to flow away from the sash bars 
and putty to the center of the runs. In ac- 
tual practice, these are relatively unimport- 
ant considerations, but all glass in the same 
run should have approximately the same 

Liquid Putty. — This is sometimes used for 
sealing cracks in old glazing or in glazing by 
the "butted" method. It may be made as 
follows: Take equal parts by measure of 
white lead, putty and boiled linseed oil. 
First, mix the putty and oil thoroughly and 
then add the lead. If it becomes too thick, 
thin with turpentin^e. 


Substitutes for Glass. — On hot beds and 
coldframes and sometimes on temporary- 
greenhouses, some transparent material 
other than glass is used. The reason for this 
is that glass is both expensive and heavy to 
handle. The most common substitutes are 
cloth and paper treated so as to make them 
waterproof and semi-transparent. Some- 
times a firm but Hghtweight white cotton 
cloth is used with no treatment, but it does 
not admit light enough to permit satisfactory- 
growth of plants for any length of time. 

Paper can seldom be used for more than 
one year. Cloth may, with care, be used for 
several seasons. The best results are secured 
by stretching the cloth or- paper on rigid 
frames or sash on which wires have been 
drawn tightly across at frequent intervals to 
serve as supports. The author has had good 
success by simply painting the cloth or pa- 
per, after stretching it over the frames, with 
pure, light, boiled linseed oil. Bailey, in the 
"Farm and Garden Rule Book," gives the fol- 
lowing recipes: 

(i) Paste stout, but thin Manilla wrap- 
ping-paper on the frames. Dry in a warm 
place and then wipe the paper with a damp 
sponge to cause it to stretch evenly. Dry 


again and then apply boiled linseed oil to 
both sides of the paper and dry again in a 
warm place. 

(2) Dissolve iH pounds of soap in a quart 
of water; in another quart dissolve i/^ ounces 
of gum arabic and 5 ounces of glue. Mix 
the two liquids, warm, and soak the paper, 
hanging it up to dry. Used mostly for 

(3) Take 3 pints pure linseed oil, i ounce 
sugar of lead, 4 ounces of white resin. Grind, 
and mix the sugar of lead in a little oil, then 
add the other materials and heat in a kettle. 
Apply hot with brush. Used for muslin. 


Probably few other structures require as 
careful or as frequent painting as do green- 
houses. This is due : First, to the moist con- 
dition of the air in the house, which favors 
the decay of the wood ; and second, to the dif- 
ference in temperature between the outside 
and inside of the house, which often causes 
excessive contraction and expansion of the 
structural material. It is especially important 
that all joints in the framework be thorough- 
ly coated when they are put together, and 
that they be well painted in order to prevent 


moisture from entering. As a rule, green- 
houses should be painted one coat both inside 
and outside every second year, and inside 
portions which are especially exposed to 
dampness and shade should be painted every 
year, care being taken to see that they are 
perfectly dry when painted. Nothing has 
yet been found which will excel pure white 
lead and oil with a turpentine dryer for this 

For the outside the intense white may be 
softened by the addition of a little lampblack 
or other coloring material, but for the inside, 
colors are avoided, as they have a ten- 
dency to absorb light. Pure white is un- 
doubtedly best for interior painting. 

Greenhouse woodwork when received from 
the factory has usually been given a priming 
coat. By special arrangement it is often pos- 
sible to have it treated in a bath of hot lin- 
seed oil or creosote. The latter will make it 

*On this point commercial greenhouse builders do not 
agree. One of the largest firms in the country uses 
a paint containing 10 per cent, of French zinc and 
finds it the most satisfactory paint they have ever 
used. Another well-known firm after experimenting 
with lead and zinc in varying proportions has gone 
back to pure lead. The tendency of zinc paints is 
to crack and peel, and of pure lead paints to become 


almost proof against decay, but since the 
joints must be coated with a thick paint 
when the house is erected, and as the wood- 
work is preferably white in order to make the 
house as light as possible, the extra expense 
involved is hardly warranted. Creosote also 
has a somewhat poisonous effect on some 
greenhouse plants. 

If the woodwork has not been primed 
when received, it is preferably so treated be- 
fore it is erected. Either pure, thin linseed 
oil, or a mixture of oil and yellow ochre is 
used for this purpose. As soon as erected, 
the whole framework is painted inside and 
out before glazing. After glazing another 
coat is applied. Because 'of the frequent 
painting necessary, it is seldom advisable at 
the time of erection, to apply more than two 
coats in addition to the priming coat. 

Paints for Iron Work. — Ordinary paints 
which are used for wood may also be used on 
most unpolished metals. The oxidization of 
iron and steel, however, is likely to stain 
white paint, unless these metals are first 
given a coating to prevent it. A good paint 
for this purpose may be made by melting to- 
gether three parts of lard and one part of 
powdered resin. This is brushed on in a thin 


layer while hot. As soon as it is dry, ordin- 
ary white lead paint may be applied with 
little danger of its becoming discolored. 
Shellac may also be used for the same pur- 

Hot water and steam pipes cannot well be 
painted with lead and oil paints on account 
of the action of the heat. One of the most 
satisfactory treatments for heating pipes is 
to paint them with the so-called "aluminum" 
radiator paint. This is light in color but 
rather expensive. Paints which dry with a 
glazed surface are said to interfere with the 
radiating properties of heating pipes. A 
dull drying black paint sometimes recom- 
menced for this purpose is a mixture of lamp- 
black and turpentine, to which linseed oil is 
added not to exceed a fourth of the bulk of 
the mixture. 

Amount of Paint Required. — ^This varies 
according to the kind and condition of the 
surface to be painted, and to some extent 
with the kind of paint used. Painters usually 
figure that a gallon of mixed paint will cover 
250 to .300 square feet of white pine or cy- 
press the first coat, and 350 to 400 square 
feet the second coat. 


A general rule for determining the amount 
required is as follows: Divide the number 
of square feet of surface to be painted by 200, 
the result will be the number of gallons of 
liquid paint required to give two coats. 

Another is: Divide the number of square 
feet by 18. The result is the number of 
pounds of pure, ground, white lead necessary 
for three coats. 

Shading. — During the summer the heat 
becomes so intense in a greenhouse that some 
shade must be given if plants are to be grown 
satisfactorily. This may be accomplished by 
the use of muslin curtains in the inside of 
the house or by lath screens laid upon the 
roof. The most common method in com- 
mercial houses is to apply some kind of a 
coating to the outside of the glass which will 
be washed off by the late fall rains. Some 
form of whitewash is most satisfactory. 

The author prefers a wash made of fresh- 
ly-slaked stone lime and water, to which is 
added one part of common salt to four parts 
of lime. The salt is added after the lime is 
slaked. This is then strained and applied 
with a spray pump. It is usually necessary 
to apply this two and often three times dur- 


ing the summer, but it comes off readily 
through the action of the fall rains and frosts 
and seldom requires the use of the scrub 

Another paint sometimes used is com- 
posed of white lead and gasoline, just enough 
lead being used to make a milk-colored 
liquid. This may be applied with a brush or 
with a spray pump. It adheres much better 
than the wash mentioned above, but is open 
to the objection that it is sometimes neces- 
sary to do considerable hand work to remove 
it in the fall. 

A third wash sometimes recommended is 
made as follows : Slake a half bushel of 
stone lime. Strain and add a brine made of 
one peck of salt in enough warm water to 
fully dissolve it. Then add three pounds of 
rice flour, and boil to a paste. Then add a 
half pound of whiting and one pound of glue 
dissolved in warm water. Mix thoroughly 
and let stand for a few days, thin with water, 
and apply. This is the whitewash com- 
monly used for painting fences and build- 
ings and is very adhesive. For greenhouses 
it is applied in a very thin coat. 

Brackets. — In glazing and painting the 



outside of a roof, a common means of sup- 
port for the workman is a plank supported 
by brackets resting on the sash bars or on 
every other sash bar. 

Glazing Ladder. — ^Another device used 
more in painting than in glazing is a ladder 

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91 i 


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Fig. 65. — Glazing ladder used in glazing and painting 

made b}^ nailing cleats on one side of a plank 
for foot holds, and on the other side longer 
cleats so that they will rest across at least 
two sash bars and thus distribute the weight. 
The ladder is held in place by hooks which 
reach over the ridge. 



Greenhouse ventilation has not yet been 
worked out with the same care and precision 
as has the ventilation of dwellings, public 
buildings, or even barns for the use of live 
stock. On the other hand, greenhouses are 
seldom or never built without some special 
attention being given to the question of 
ventilation, whereas, dwellings and even 
public, buildings are often erected without 
any reference whatever to this important 

This anomaly may be partly explained by 
the following facts: (i) The transpiration of 
plants is not so well understood nor is it so 
easily measured as is the transpiration of ani- 
mals. (2) Windows are necessary in dwell- 
ings and public buildings to admit light and 
they may be utilized, when necessary, to pro- 
vide ventilation. (3) In greenhouses, ventila- 
tion is not only provided for the purpose of 



maintaining a supply of fresh air, but is 
utilized as a method of controlling tempera- 
ture and humidity. (4) Greenhouses, be- 
cause of their transparent roofs, are much^ 
more liable to sudden or violent changes in 
temperature (especially in days of alternate 
clouds and sunshine) than are dwellings, and 
the necessity for ventilation in order to 
equalize the temperature is evident. (5) 
Greenhouse plants are, as a rule, particular- 
ly sensitive to cold drafts, and ventilation 
cannot be left to the indiscriminate opening 
of doors. 

Systems of Greenhouse Ventilation. — 

There can hardly be said to be any well de- 
fined systems of greenhouse ventilation, as 
compared with the so-called systems of 
ventilation for public buildings* Greenhouse 
ventilation rests on the 'principle that warm 
air has a tendency to rise, and since the air 
within the greenhouse is considerably warm- 
er than that outside, during both summer 
and winter, the question of changing the air 
presents no serious problem. It is only 
necessary to provide a means for the warm 
air to escape. The cooler air from the out- 
side easily finds its way into the house 



through the numerous small openings be- 
tween the panes of glass. 

Side Ventilation. — Side ventilation is of 
little service, except during the summer 
months, as the opening of these ventilators 
in winter would expose the plants to a direct 

Fig. 66.— Greenhouse showing A, side ventilators; 
B, overhead or roof ventilators 

current of cold air which would prove fatal. 
Side ventilating sash are usually hinged at 
the top and open outward and upward. 
Probably less than 50 per cent, of the com- 
mercial houses in the country are equipped 
with side ventilation, though it is often con- 


venient in spring and summer. An in- 
genious method is sometimes employed in 
conservatories whereby the air is taken in 
from below the benches and is warmed by 
passing over the heating pipes. Thus the 
danger of injury to the plants is greatly less- 
ened. There is no evidence to show that 
there is any special benefit to be derived from 
these ventilators (Fig. 67). 

Overhead Ventilation. — During the winter 
practically all the ventilation of greenhouses 
is accomplished by means of overhead 
ventilators set in the roof at or near the 
ridge. These ventilators are in the form of 
sash hinged on the outside, and may be 
closed down tightly over the sash bars or 
opened to any degree desired. As the warm 
air naturally rises, the opening of these 
ventilators allows the warmest air of the 
house to escape, and fresh cool air to' filter 
in through the crevices between panes of 
glass without causing excessive drafts. 

Experience shows that these ventilators 
need to be relatively narrow and practically 
continuous along the whole length of the 
house, rather than intermittent, as the pres- 
ence of occasional large openings is more 




likely to cause drafts of cold air. They are 
preferably glazed with glass of the same 
width as used for the roof and they should 
be placed so that the bars of the sash will 
be directly over the sash bars. 

Size of Ventilators. — No definite rule can 
be given as to the size of ventilators, as so 
much depends on the location and arrange- 
ment of the house, the kind of plants to be 
grown, etc. Experience has shown that 
where the ventilators are continuous along 
the entire length on both sides of the roof, 
the following sizes are sufficient. 

Size of house Width of ventilating sash 

Up to 40 feet wide 24 inches 

Above 40 feet wide 30 inches 

This is the rule followed by most green- 
house builders. 

Methods of Hanging Sash. — Ventilating 
sash may be hung so as to open either at the 
top or bottom; that is, they may be hinged 
at the lower side so as to open out and away 
from the ridge, or they may be hinged at the 
ridge so as to open upward from the lower 
side. Both methods have their advantages 
and disadvantag^es. Sash opening at the 
ridge have the advantage that the air will 



escape more rapidly when the ventilators 
are opened, as there is but little obstruc- 
tion and the opening is at the highest part 
of the house. There is also less tendency, 
when ventilators are used on one side of 

Fig. 68. — Two methods of hanging ventilator sash 

the roof only, for unfavorable winds to 
blow directly into the house. 

The practical disadvantages of this meth- 
od of hanging is that the ventilator sash 
are more likely to be torn off by severe storms 
than when hinged at the top, and also that 
it is more difficult to prevent leakage at 
the ridge. The prevailing tendency is to 


hinge the sash at the ridge and in houses 30 
feet wide or more to provide ventilators on 
both sides of the roof. 

Operating Machinery. — Since the ven- 
tilating sash are placed at the highest part 
of the house, and as it is necessary to change 
the size of the opening several times a day, 
it is obvious that it is highly desirable that 
some method be provided by which they may 
all be opened and closed from some point 
convenient for the operator. This is accom- 
plished by means of various types of sash- 
operating machiney. 

The essential features on which most 
types of ventilating machinery depend are 
as follows: (i) A horizontal shaft firmly 
fastened near the line of ventilating sash; 

(2) a system of gearing, by which power ap- 
plied at a point convenient to the operator 
may be transmitted to and rotate this shaft ; 

(3) arms or levers attached to the shaft and 
also to the sash," and so arranged that the 
sash are raised or lowered when the shaft 
is rotated. 

Shafting. — The shafting generally used is 
one inch or one and a fourth inch gaspipe. 
The lengths are either riveted or clamped 


together by special couplings so that the 
shaft will be perfectly rigid. A method 
sometimes used is to screw the lengths of 
pipe into an ordinary sleeve coupling as 
far as they will go ; drill a hole through each 
end of the coupling and pipe, and rivet all 
together with tight-fitting rivets. This 
method is less satisfactory, however, than 

Fig. 69. — Malleable iron shaft couplings 

the use of split malleable iron castings sev- 
eral forms of which are to be had. These 
castings are longer and stronger than the 
usual sleeve coupling and they thus have a 
firmer grasp on the pipe. 

They usually have pins or lugs cast in 
the inside which fit into holes drilled in the 
pipe at the proper positions, and the two 
parts are clamped tightly in place by means 
of bolts. A special advantage of this meth- 



od of coupling is that the shafting may be 
put up in sections and clamped together after 
being put in place. Square or round, solid 
shafting is sometimes used, but it has less 
torsional or twisting strength, weight for 
weight, than does good wrought-iron or 
steel pipe. Wrought pipe comes in two 
weights, standard and extra heavy. It is 
safe to use the different sizes and strengths 
as follows: Shafts up to 50 feet in length, 
I inch standard strength; shafts up to 75 
feet in length, 40 feet of i inch extra heavy, 
and 35 feet standard strength; shafts up to 
125 feet in length, i/4 inch all extra heavy. 

Shaft Hangers. — The shafting is held in 
place by means of hangers. These hangers 

Fig. 70.— Shaft hangers 

may be fastened to the rafters, to the sash 
bars or to the supporting posts. In iron frame 
houses it is customary to hang overhead 
shafting from the rafters and the shafting 
for the side ventilators from the side posts, 
using a hanger for each rafter or post. 



When the shafting is hung from the sash 
bars a hanger is attached to every second 
or third bar, usually to every second. 

Fig. 71.— 
Open col- 
umn ventil- 
ator gearing 

Fig. 72.— 
Open col- 
umn chain 

Gearing. — Generally speaking, there are 
three types of gearing utilized for operating 
overhead ventilator shafting. These are: 
(i) The column gear, of which there are 
many different forms; (2) the chain-oper- 



ated gear; and (3) the rack and pinion gear. 

In the column gear a post or column sup- 
ports the gearing and the wheel to which 
the power is applied. One form of column 
gear is known as an open column 
gear, because the drive rod is not 
inclosed in the column and there 
is no housing about the gearing. 
In another open column gear 
type a chain is used to transmit 
the power. In the closed col- 
umn types all gearing is inclosed 
and runs in oil, much the same as 
in the transmission case of an 
automobile. This insures free- 
dom from noise and ease of 

In the chain type no columns 
are required, a feature much 
prized by growers. By this sys- 
tem practically all the ventilators 
in a house may be operated from 
one point, as the chains may be 
run almost anywhere in the house 
by the use of pulleys. The ab- 
sence of columns means less shade. 

The rack and pinion type differs from 
the two general types mentioned above, not 
so much in the method of applying the power 

Fig. 7Z.— 
Qosed col- 
umn ventil- 
ator gearing 



Fig. 74. — Chain system of operating ventilators. No 
columns used 

Fig. 75. — Rack-and-pinion system of operating 


to the shaft as in the method of actually 
opening the ventilators. The chief advan- 
tage of this system lies in the fact that there 
is less torsional or twisting strain on the 
shafting than when the usual method is em- 
ployed, and they are more powerful. The 
chief disadvantage is that provision must be 
made for giving the shaft several revolutions, 
while a half or two-thirds revolution is usual- 
ly sufficient with the more common forms. 

Some practical growers claim that the rack 
and pinion device is very subject to Wear and 
is a frequent cause of trouble. This is more 
especially true of the older forms of this type. 
The fact that they are not generally used 
would seem to indicate that practical growers 
as a rule are not yet convinced of their super- 
iority, though they are now being installed in 
some large houses where it is necessary to 
operate long runs. 

Quite frequently the hand wheel and gear- 
ing are fastened to the rafters or purlin posts 
and no extra columns are required. 

Side Ventilating Machinery. — The essen- 
tial features of side operating machinery 
are the same as for overhead ventilators. 
When there are side benches a shaft is 



Fig. 76. — Ventilators (a and b) operated by means of 
rods with universal joints attached to posts and 
rafters. No extra columns are necessary. 

usually used and the hand wheel placed at a 
convenient position for the operator. When 
there are no benches along the sides a com- 
pact device is advisable in order to take up as 
little room as possible (Fig. 78). 



Fig. n , — Device for 
operating side ventilators 

Ventilator Arms. — 

Ventilator sash are 
most commonly raised 
and lowered by means 
of hinged braces or 
arms operated from 
the shafting. There 
are three general 

The elbow arm is 
most commonly used 
but has the disadvan- 
tage that a long lever- 
age is required, in order to open the venti- 
lators to the full width, which puts a consid- 
erable strain on the shaft. 

The double acting arm overcomes this dif- 
ficulty to some extent as it is possible to se- 
cure a wider opening with a shorter leverage, 
but it is necessary to rotate the shaft 
through an extra half turn. On long runs 
these arms are now being extensively used in 
place of the common elbow arm. 

The extending arm is used in low houses, 
or for side ventilators, or in other places 
where an elbow or double acting arm would 
extend into the house so far as to be in the 


way. It folds together when the sash is 
closed and occupies little space, but it ex- 
tends automatically when the shaft is turned. 
It is especially convenient under certain con- 
ditions, but it lacks the strength necessary 
for long runs. 

Fig. 78. — Compact machine for operating side ventilators 

In all systems the arms are clamped se- 
curely and rigidly to the shafting, and as 
near as possible to the hangers so as not to 
spring the shafting when heavily loaded. 
They are spaced about 3 feet apart along the 
sash. If continuous sash are not used the 
arms should be distributed as follows: For 
sash up to 4 feet long, oji^arm ; from 4 to 7 



Fig. 79. — Types of ventilator arms. A, double acting 
arm; B, elbor,v arm; C, extending arm closed; D, extend- 
ing arm open 


feet long*, two arms; and from 8 to ii feet 
long, three arms, etc. 

Capacity of Ventilating Apparatus. — The 
capacity of ventilating apparatus depends 
largely upon the size and method of manu- 
facture, but the length of run is limited to 
the torsional strength of the shafting. In 
long lengths there is always more or less tor- 
sion, so that the ventilators at the extreme 
end do not open as wide as those close to 
where the power is applied. This is of little 
consequence in summer when the ventilators 
are wide open, but in winter, when only 
slight ventilation is required, it may result in 
the sash at the end of the shaft not open- 
ing at all and the ventilation will thus be un- 
even and unsatisfactory. Moreover^ the sash 
are likely to be frozen down in winter and 
the tendency for the shafting to twist is thus 
increased. It is wise to have a wide margin 
for safety. 

An indication of the length of shafting 
that may be used with safety is given on 
page 130. Tests show that one and a 
fourth-inch standard pipe has a torsional 
strength 42 per cent, greater than i-inch 


double-strength pipe and that the weights 
are practically the same. The price of i- 
inch double-strength pipe averages about 25 
per cent more than standard one and a fourth 
inch pipe. It is evident, therefore, that for 
long runs it is not only safer but more 
economical to use one and a fourth-inch 
standard pipe than i-inch double-strength. 

Generally speaking, a 150-foot run is about 
the limit when elbow arms are used. This 
may be slightly increased by using the 
double acting arms, and still further by us- 
ing the rack and pinion system. This is 
equivalent to saying that the ventilators in a 
house 300 or 350 feet long may be operated 
from one station by having machines located 
in the center of the house and operating each 
way. It is economy to have all ventilator 
sash for one house operated from the same 
station if possible. 

Sliding Shaft System. — In order to enable 
the operator to care for an extremely long 
line of sash from one station a sliding shaft 
system has been devised. In this case the 
shafting is solid and square, and instead of 
rotating it slides backward and forward, the 
motion being given by a pinion working on 
a screw or worm gear at one end of the shaft. 




Fig. 80. — Sliding- shaft system for operating ventilators 

This sliding movement is utilized to 
operate the sash by means of a right angle 
lever, pivoted at the angle with the short arm 
attached to the shaft and the long arm to the 
sash. It is claimed for this system that it 
will operate a line of sash 500 feet long. 


In the earlier greenhouses, plants were al- 
most always grown on raised benches. This 
was partly for the convenience of the grow- 
er and partly because the houses were almost 
always erected with high, solid side walls 
and it was necessary, in order to secure satis- 
factory growth, to bring the plants close to 
the glass roof. In modern houses, when all 
or part of the side walls are of glass, raised 
benches are not so necessary, and are very 
commonly dispensed with and the plants 
grown directly in the soil which forms the 
floor. This is particularly true when vege- 
tables such as lettuce, tomatoes or cucum- 
bers are grown. 

Florists, as a rule, have been loth to give 
up the use of benches and present the follow- 
ing arguments in their favor, (i) It is 
more convenient to care for plants when 
grown on raised benches than when grown 
on the ground. (2) Benches make possible 




the placing of the heating pipes underneath, 
which makes them less conspicious and at 
the same time affords a method of giving 
"bottom heat/' which is considered advant- 
ageous with many plants. (3) It is main- 
tained that there is a better circulation of 
air about plants grown on benches and that 
the plants are less subject to disease. (4) 
The temperature and moisture of the soil 
can be more easily regulated in benches. 
(5) Low-growing plants make a better dis- 
play when grown on benches. 

The following are the most common dis- 
advantages claimed by those who urge 
against the use of benches, (i) They are 
expensive to build and maintain. (2) They 
do not admit of an economical use of space. 
(3) The soil dries out rapidly. (4) The soil 
has to be changed rnore often. (5) It is 
more difficult to use labor-saving tools such 
as wheel-barrows. (6) All work must be 
done by hand. In large houses it is possible, 
when plants are grown on the ground, to pre- 
pare the soil with a horse or with wheel hoes. 
(7) With high-growing plants such as to- 
matoes and cucumbers, it is difficult to har- 
vest the crop when they are grown on high 


Fig. 82. — Tomatoes growing in solid raised beds 

Fig. 83. — Solid raised beds of hollow building tile in use 
at the Michigan Agricultural College 


Raised Beds. — To overcome some of the 
objections to raised benches, many growers 
use solid raised beds, the height varying from 
a few inches to that common for benches. 
Such beds dry out less quickly than do 
benches, the soil does not have to be removed 
as frequently, and they are less expensive to 
maintain. They are open to some of the ob- 
jections urged against benches and do not 
possess many of the advantages afforded by 
culture in the open soil. The width and ar- 
rangement follows closely that of benches. 

Raised Benches. — Benches are exposed 
continuously to conditions which favor their 
rapid deterioration. Unless well constructed 
of good material, they are a source of con- 
stant annoyance. Many growers use wooden 
benches. Others use benches having iron 
frames, and sides and bottoms of wood, tile, 
slate or cement slabs. Still others use solid 
concrete benches. All forms have their ad- 
vantages and their advocates. 

Wood Benches. — Wood benches have the 
advantage of slightly less first cost, though 
if good material is used, the cost will be near- 
ly as great as for iron frame benches. In 
permanent houses nothing but cypress or 


cedar should be used, genuine pecky cypress 
being undoubtedly the best. The sides 
and bottom boards are not less than i inch 
thick. The side boards are 8 inches wide. 





Fig. 84. — Two types of wood benches. A, bottom boards 
running lengthwise; B, bottom boards running crosswise 

The width of the bottom boards is imma- 
terial, except that when in place they have a 
space of a fourth-inch between them for 
drainage. They are usually run length- 
wise of the bed and are supported by cross- 
beams, spaced not more than 4 feet apart. 

The size of the cross beams will depend 
somewhat on the width of the bench, as 
follows : 

For benches up to 4 feet wide 2x4 inches 

For benches from 4 to 6 feet wide.... 2x6 inches 
For benches over 6 feet wide 2x8 inches 

The legs or posts are at least 4x4 inches 
in size, and rest on concrete or brick piers. 
Sometimes, when cement walks are used, 
they are made to extend under the benches 
far enough to act as a foundation for the 



To guard against warping of the side and 
end boards of wood benches, angle irons 
may be used in the corners and along the 
sides, and fastened by screws or small bolts. 
Brick piers may be used in place of the 
wooden legs. The wooden legs, however, 
will usually outlast the bottom boards and 

Fig. 85.— A type of iron frame bench 

Iron Frame Benches. — In the majority of 
iron frame benches, i-inch wrought-iron 
pipe is used. It is rarely threaded but is tied 
together with split malleable iron castings 
by the use of bolts and set screws. The 
sides and bottom may be made of wood, iron, 
slate, tile or even of cement slabs. All are 


removable and may be replaced without tak- 
ing down the frame. 

Iron frame benches with cypress sides and 
bottoms are now much in favor. They are 
but little more expensive than the all-wood 
benches and are in most cases more satis- 
factory, as the frames are nearly indestruct- 
ible. They should, however, be made of 
wrought-iron pipe rather than of steel. 
They may be had in two forms, one in which 
the bottom boards run lengthwise of the 
bench and another in which they run cross- 
wise. The advantage of the latter is that 
short lengths may be used. These benches 
may be purchased with all parts cut to order, 
or they may be easily cut by anyone familiar 
with pipe cutting. 

Iron frame benches are also made of angle 
iron or structural iron of different forms. 
The chief disadvantage of these is that the 
iron cannot be worked readily by the ordin- 
ary workman and must be cut and fitted at 
the factory. 

Concrete Benches. — Concrete, because of 
its permanency, is often recommended for 
greenhouse benches, and its use is increas- 
ing. In general, there are two separate 




types. In one type the legs, bottom and 
sides are cast separately in molds and then 
put together in the greenhouse. In the other 
type the whole bench is cast in a form built 
in the house where it is to stand. There 
are at least two firms having patents on 
cement greenhouse benches and who are pre- 
pared to sell or rent molds or forms for mak- 
ing them. It is also possible for a skilled 
mechanic to make forms to suit any special 
location or for any form of bench. In mak- 
ing concrete benches, care should be taken 
to provide for adequate drainage through the 
bottom and to see that they are thoroughly 

There has been some discussion as to the 
effect of concrete benches on the growth of 
plants. The author has had but little prac- 
tical experience with them but quotes from 
one of the largest users of concrete benches 
in the country, as follows: 

"At my place I use only concrete benches 
and the results and advantages .have been 
very satisfactory, but I want to be open and 
frank concerning the disadvantage, which is 
only for the first year. Something in the 
line of a chemical of a whitish nature ap- 
pears on fresh new cement, and that seems 


to be injurious to plants; but after you have 
filled the benches with soil and used them 
the first year, the soil generally eats or ab- 
sorbs this chemical, and the roots of carna- 
tion plants or anythmg else cling to the ce- 
ment slabs the same as they do to slate. A 
good remedy to get rid of this so that it will 
not injure the plants is simply to put air- 
slaked lime or rather heavy whitewash on 
the inside of the bench, and that seems to 
protect the plants from coming in contact 
with the chemical mentioned.'* 

Height and Width of Benches.— The 
height of greenhouse benches is largely de- 
termined by that most convenient for 
the operator to work. This in turn depends 
upon the nature of the plants to be grown. 
For example, when low-growing plants like 
lettuce are grown, a bench 32 inches high is 
about right ; but when carnations are grown 
this may be so high as to make disbudding 
difficult. This refers to the distance from 
the top of the walk to the top of the sides 
of the bench. 

The width of the bench depends on the 
width of the house, on the arrangement of 
the benches, and to some extent on the kind 


of plants to be grown. It is limited to the 
distance a man can conveniently reach in 
caring for the plants. This distance is 
about 2>^ feet or rarely 3 feet. In other 
words, benches that can be worked from 
one side only should be no more than 2}A or 
3 feet wide, and benches which may be 
worked from both sides should be no more 

Fig. 87. — Method of arranging benches in an uneven- 
span house to secure best advantage of the sunlight 

than 5/^ or rarely 6 feet wide. In uneven 
span houses it is sometimes advisable to ele- 
vate the walks and benches. 

Arrangement of Benches. — This is gov- 
erned by the width of the house, the use for 
which the house is designed, the height of 
the beds or benches and by the individual 
preference of the owner. Commercial grow- 



ers look upon walks as waste space and en- 
deavor to keep them as narrow as is con- 
sistent with ease and economy in getting 
about the houses. In private houses, con- 
servatories and show houses, the walks are 
sufficiently wide to allow two persons to pass 

Fig. 88. — An arrangement of benches in a 30Lfoot house. 
Only 66 2-3 per cent of the floor space 
available for crops 

In figures 88 and 89 are illustrated two 
methods of arranging benches in a 30-foot 
house. By the first method four benches, 
each five feet wide, are provided and 661 per 
cent of the floor space is available. By the 
second method three wide and two narrow 
benches are provided and 73* per cent of the 
floor space is available. In the latter method 


the side benches extend the entire length of 
the house and one walk is eliminated. 

It is worth while to exercise considerable 
care in determining the arrangement of 
the benches, especially in commercial houses. 
As a rule a walk along the side of a house 
is an extravagance. When the width of the 

Fig. 89. — ^Another arrangement of benches in a 30-foot 

house. By this arrangement IZ 1-3 per cent of the floor 

space is available for growing crops 

house admits, it is usually more economical 
to have narrow benches along each side. 

When low beds are used, the walks may 
be narrower than with high benches as peo- 
ple can pass more readily. In conserva- 
tories and show houses 3 feet is none too 


wide. In commercial houses with high 
benches, from 20 to 24 inches is a common 
width. When low beds are used, the walks 
are sometimes as narrow as 14 or 16 inches. 
It is often advisable to arrange the 
benches so as to have the center walk of ex- 
tra width, which will allow of the use of 
a wheel barrow or ^art in removing and re- 
plenishing the soil and for other purposes. 

Material for Walks. — Concrete is unques- 
tionably the best material for walks. Water 
has no effect on it; it is substantial; it may 
be used as a foundation on which bench legs 
and ventilator columns may stand; and it 
may be quickly and easily laid. In conserv- 
atories and private houses nothing can take 
its place. For data on concrete construction 
see Chapter XIV. 

In commercial houses coal ashes are often 
used. Ashes must be kept away from the 
pipes as the sulphur they contain will cause 
the pipes to corrode very rapidly. 

Curbs. — For convenience and cleanliness, 
many growers who plant directly on the 
ground prefer to have their houses marked 
off into regular beds, divided by narrow 
walks and surrounded by a curb to keep the 


soil in place. In time, the constant addition 
of manure raises the soil in these beds so 
that they become in reality raised beds. 
Board or plank curbs are rarely satisfactory, 
as the moisture of the soil on one side causes 
them to warp. The most satisfactory and 
economical curbs are made of concrete, 
which is heavily reinforced with iron rods 
when it is poured. 


Generally speaking, there are only two 
satisfactory methods of greenhouse heating: 
Steam and hot water. Direct heating by 
stoves is not satisfactory even in small 
houses, and no satisfactory system has yet 
been devised for the use of hot-air furnaces. 
The only method aside from steam or hot 
water which deserves mention is heating by 
flues. They are wasteful of fuel, and their 
use is not justified, except in cheaply con- 
structed houses which are used only for a 
few months in the spring or fall. 

The principles pertaining to greenhouse 
heating are much the same as those involved 
in heating other buildings, except that the 
loss of heat is greater from glass than from 
wood or brick walls, and a higher and more 
constant night temperature is required than 
is necessary in dwellings. For this reason, 
relatively more radiating surface is required 
and boilers of larger capacity are needed. 



Heating with Flues. — In heating with 
flues the equipment consists simply of a 
furnace at one end of the house and a chim- 
ney at the other, the two being connected by 
a flue, carried underneath the bench or 
buried just underneath the soil, through 
which the heat and smoke are carried. This 
may be made of brick, but large-size drain 
or sewer tile are more commonly used. These 
withstand the heat and are easily and cheap- 
ly put in place. It is best to have the flue 
slope upward slightly toward the chimney. 
As has already been stated, this rnethod is 
wasteful of fuel. It is also difficult to regu- 
late. It is still employed to some extent 
by vegetable gardeners in cheap houses, 
used only in late winter or early spring for 
the starting of early vegetable plants, sweet 
potatoes, etc. 

Hot Water vs. Steam. — There has been 
much discussion as to the relative virtues of 
hot water and steam for use in greenhouse 
heating. It may be well to consider here 
some of the advantages claimed for each. 
For hot water the following are claimed: 
(i) It provides a more even heat than steam. 
(2) The radiating pipes are not so hot, and 


plants near them are less likely to be injured 
than when steam is used. (3) It requires 
less frequent firing, since warm water is al- 
ways circulating in the pipes as long as there 
is any fire in the furnace, whereas, with 
steam it is necessary to keep the water boil- 
ing to keep steam in the pipes. (4) For the 
above reason a night fireman is not required 
in small houses equipped with hot water. (5) 
It is less dangerous. This is more apparent 
than real, for steam is usually carried at low 
pressure. (6) It is claimed that hot water 
requires less fuel. Theoretically this should 
be true, but in practice it has not been very 
definitely proven. (7) Water will hold heat 
for some time if the fire should accidentally 
go out. 

The following advantages are claimed for 
steam: (i) Less cost of installation. (2) 
Steam requires fewer radiating pipes hence 
less shade is cast when the pipes are placed 
overhead than when hot water is used. (3) 
Less time is required to get up heat, as there 
IS a relatively small body of water. (4) A 
greater area may be warmed from a given 
heating plant than with hot water, for the 
steam may be forced farther. (5) A steam 


plant may be used to furnish steam for soil 

All the above apply more especially to 
small ranges than to large ranges. As a 
rule, hot water is more generally used in 
ranges covering up to 20,000 square feet and 
steam in larger ranges, although there are 
many exceptions. At present the tend- 
ency seems to be toward the use of hot water 
rather than steam. 

In an investigation recently made by the 
author among a large number of greenhouse 
owners, 86 per cent, of those having 20,000 
square feet or more under glass preferred 
steam heat. The chief reasons stated were, 
"better control," "cheaper maintenance," and 
"less shade from pipes." Six per cent, pre- 
ferred a combination of hot water and steam. 
The remaining 8 per cent, preferred hot 
water, stating as their reasons, "steadier 
heat," "plants grow better," "pipes do not 
rust out during the summer as with steam," 
and "cheaper to operate in spring and fall 
when little heat is required." 

Of those having less than 20,000 square 
feet under glass, 74 per cent, preferred hot 
water, giving in addition to the reasons 




named above, "less labor to fire, especially at 
night'' and "needs no night fireman/' 

Combination Systems. — A combination of 
hot water and steam may often be used to 
advantage. By this means steam may be 
had for power and at the same time be util- 
ized for heating. In cold weather both boil- 
ers may be used for heating, while in mild 
weather the steam boiler alone may be used, 
thus furnishing the necessary heat and 

Another and more simple combination of 
hot water and steam heating which, how- 
ever, is more expensive in installation, con- 
sists of two separate sets of heating coils, 
one of which is connected with a steam boil- 
er and the other with a hot water boiler. The 
steam is used when a small amount of heat 
is needed quickly on cold nights in early fall 
or late spring, and to supplement the hot 
water in severe winter weather. 

In any system of heating it is much safer, 
as well as more economical in operation, to 
install two or more boilers rather than to 
depend on one large one. Both may be 
used in severe weather and in case of acci- 
dent to one, the other may be forced for a 


few days and thus protect the plants from 
injury by freezing, which would inevitably 
result if only one boiler was in use. 

Heating Coils. — Because of the large 
amount of heating surface required, and be- 
cause all parts of a greenhouse must be kept 
at as nearly uniform temperature as possible, 
radiators such as are used in private houses 
have not been found practicable in green- 
house heating. Instead, long coils of 
wrought iron or steel pipe are used. For 
steam heating these coils are commonly of 
I or I /4-inch pipe. In hot water heating they 
are slightly larger, varying from i% to 2 
inches. In the early days of hot water heat- 
ing large cast-iron pipe, often as large as 
four or five inches in diameter was used. It 
is still used to some extent, but more often 
in small private conservatories than in com- 
mercial houses. 

There is very little to be said in favor of 
using cast-iron pipes. The fact that they are 
now so little used shows that they have no 
special merit. The smaller, wrought pipe is 
lighter and much more easily handled; is 
screwed together instead of caulked with 
lead and oakum; has much more radiating 



surface in proportion to the volume of water 
contained; can be placed along the side 
walls or hung on the supporting posts in- 




*^ ^ •* -'^S 



Fig. 91. — Under-bench heating with large cast-iron 

Stead of having to be supported on mason- 
ry piers ; and permits of a more perfect con- 
trol of the heat. 


Heating coils are made by joining several 
pipes together by means of headers. The 
hot water is conducted to the coils from the 
boiler by means of a larger pipe known as 
a flow pipe or feed pipe. It is returned to 
the boiler by means of a return pipe. In 
steam heating the coils are often so arranged 
that the water formed from the condensed 
steam returns to the boiler through the flow 
or feed pipe, instead of through a separate 
return pipe. 


General Principles. — Before discussing 
the installation of a hot water heating sys- 
tem it is necessary to have in mind the phy- 
sical and mechanical principles involved. 
Briefly they are these: Water increases in 
volume as it is heated and it is consequently 
lighter in weight. When a fire is lighted un- 
der a water boiler the water around the heat- 
ing surface expands and, being lighter, is 
forced upward by the heavier, colder water. 
Popularly speaking, the hot water "rises." 

The practical problem is to conduct the 
hot water from the boiler to the coils where 
the large radiating surface permits the water 
to give up its heat to the air in the house 
and then, as it becomes colder and heavier, 
to conduct it back to the boiler where it will 
displace the warmer and lighter water there. 
Gravity is the force utilized to produce cir- 
culation. It acts with a force proportional 
to the difference in weight between the col- 
umn of warm water and the column of cool 



The following table shows the weight of a 
cubic foot of distilled water at different 

32 degrees F. .62.42 pounds 170 degrees F. .60.77 pounds 


. . .62.02 " 




...61.89 " 




...61.74 ** 




...61.56 " 



140 " 

. . .61.37 " 

220 '* 


150 " 

....61.18 " 




. . .60.98 " 

From the above table it is apparent that a 
cubic foot of water entering the boiler at 140 
degrees is 0.82 pounds heavier than an equal 
quantity leaving the boiler at 180 degrees. 
It is evident that the higher the columns of 
water the greater will be the difference in 
weight, and consequently the more rapid will 
be the flow. 

The various factors influencing the veloc- 
ity of water in a gravity hot water system 
are embodied in the following formula. 


2gh (w— W) 


In this formula, V=the velocity in feet per 
second, g=the force of gravity (32.16), h= 
the total height of the system, W=the weight 
of a cubic foot of water when it leaves the 


boiler and w=the weight of a cubic foot of 
water when it enters the boiler. 

This, of course, disregards friction. The 
practical application is that when it is de- 
sired to increase the velocity of the water; 
e.g. in long runs, it may be done by either 
lowering the boiler or by raising the height 
of the flow pipes. 

The following table shows the velocity in 
feet per second in a hot water system under 
various conditions. 

DiflFerence in temperature on leaving and 
entering boiler 
10° 15° 20° 30° 40° 

Feet Per second 
0.750 0.922 1.09 
1.06 1.32 1.55 

1.50 1.85 2.19 

1.83 2.26 2.68 

Arrangement of Piping. — There are two 
approved methods of arranging the piping 
for hot-water heating. One is known as the 
*'down hill"; the other as the "up hill." In the 
former the highest point in the system is 
directly above the boiler. In the latter the 
highest point is at the end of the system 
farthest from the boiler. Either is satisfac- 
tory and is preferred to the "level" system 
sometimes advocated. In either the "down 






5 ft. 


10 " 


20 " 


30 " 












hiir' or the ''up hiir' system the air which 
collects in the pipes will eventually reach the 
highest point when it may be allowed to 
escape through an automatic air valve. In 
the "level" system slight sags and raises are 
likely to occur and the air will collect in the 
higher parts and cause trouble. 

--- A' 

Fig. 92. — Diagram showing "down-hiH" and **up- 
hiir* systems of 'piping. A, boiler; B, flow pipe; 
C, C, headers; D, radiating pipes or coils; E, re- 
turn pipe; F, automatic air valve; x indicates 
height of water column 

The author prefers the "down hiir* system 
when the flow pipes are carried in the upper 
part of the house and the coils are consider- 
ably lower. When all the pipes must be in 
the lower part of the house, or under the 
benches, he prefers the "up hill" system. The 



Fig. 93.— A type 
of automatic air 

majority of greenhouse oper- 
ators seem to be in accord 
with this view. Practically- 
speaking there appears to be 
but little difference in the 
efficiency of the two systems 
and the convenience and the 
arrangement of the house de- 
termines the choice to a con- 
siderable extent. 

Estimating Radiation. — 
The calculations for green- 
house heating are based on 
certain fundamental facts which for hot 
water may be stated briefly as follows: A 
square foot of glass will give off, under or- 
dinary greenhouse conditions in winter 
weather, approximately i B. T. U* of heat 
per hour, for each degree difference in tem- 
perature between the air inside the green- 
house and that outside. A good wood, brick 
or concrete wall will give off about a sixth 
as much, or a sixth B. T. U. per square foot 
per hour. It is customary to divide the total 
wall surface by six and consider it as equiva- 
lent to glass. 

♦British Thermal Unit; the amount of heat required to 
raise one pound of distilled water from 62 to 63 
degrees F. 


To arrive at an estimate of the possible 
heat loss from a greenhouse add to the total 
square feet of exposed glass surface a sixth 
of the total square feet of exposed wall sur- 
face, and multiply the sum by the difference 
between the temperature at which the house 
is to be kept and the lowest outside tem- 
perature which will probably be experienced. 
Suppose, for example, that a house has 
10,000 square feet of glass and equivalent 
glass, that it is desired to keep it at a night 
temperature of 50 degrees, and that the low- 
est outside night temperature to be expected 
is — 10 degrees. The number of B. T. U. 
given off by such a house under these con- 
ditions would be [50°^ — ( — 10°)] x I x 10 X 
10,000 or 600,000 B. T. U., and enough heat- 
ing coils must be provided to supply this 

In hot water heating the coils will give 
off approximately two B. T. U. per square 
foot of surface per hour for every degree 
difference in temperature between that of 
the coil and that of the surrounding air. The 
average temperature of the coils may be 
taken to be 160 degrees, and if the house is 
to be maintained at 50 degrees the difference 
will be no degrees. Multiplying no by 2 


we have 220 or the number of B. T. U. given 
off by each square foot of radiating surface 
per hour. If, then, we divide 600,000 by 
220 we have 2,727 which is the number of 
square feet of radiating surface to be pro- 

These principles may be embodied in the 
following formula where R= the amount of 
radiating surface required in square feet; T, 
the temperature to be maintained inside the 
house; t, the lowest outside temperature to 
be expected; and G, the number of square 
feet of glass and equivalent glass. 

(T-t) X G 
(160-T) 2 

This formula gives a wide margin of safe- 
ty. Most builders prefer to use consider- 
ably less radiating surface and depend on 
forcing the furnace in extremely cold 
weather. By so doing the temperature of 
the coils may be kept at 180 degrees or even 
considerably higher under favorable condi- 
tions and the amount of radiation required 
will be correspondingly less. 

Amount of Pipe Required. — Having esti- 
mated the amount of radiation required the 
next problem is to find the quantity of pipe 


necessary to provide this amount. For ex- 
ample, I linear foot of i>4-inch pipe furnishes 
about half a square foot of radiating surface. 
Divide the number of square feet of radia- 
tion required by the outside area of a linear 
foot of pipe of the desired size. The result 
will be the number of linear feet of pipe re- 
quired. From this is subtracted the 
amount of radiation supplied by the flow or 
feed pipe and other fittings. 

The following table gives the radiating 
area in square feet of a linear foot of pipe of 
various sizes. 

Radiating surface of 
Size of pipe 1 linear foot 

V4 inch 0.27 square feet 

1 " 0.35 

IK " 0.43 

VA " 0.49 

2 " 0.62 

2^ " 0.75 

3 " 0.91 

3^ " 1.05 

4 " 1.18 

For practical purposes the following gen- 
eral rule will give approximately the 
amount of radiating surface required. Divide 
the number of square feet of glass and 

equivalent glass : 

By 6 to heat the house to 40 degrees 
By 4 to heat the house to SO degrees 
By 3.5 to heat the house to 60 degrees 
By 3 to heat the house to 70 degrees 

The quotient will be the square feet of 
radiating surface required. 

Size of Flow Pipe. — Having determined 
the amount of radiation necessary, the next 
problem is to determine the size of the flow 
or feed pipe required to supply the coils. 
Experience has shown that it is not necessary 
for the supply pipe to be equal in capacity 
to the sum of the capacities of the coil pipes. 
The correct size may be determined, theo- 
retically, by the use of the following rather 
tedious formula: 

A= 5l^ 


In this formula A=the cross section 
area in square inches of the flow pipe; 
H, the total radiation in B. T. U. per 
hour given off by the coils ; R, the radiating 
surface in square feet; w, the weight of the 
water per cubic foot; v, the velocity of feet 
per second; t, the difference in temperature 
between the water when it leaves the boiler 
and when it returns. 

This formula is seldom used but the fol- 


lowing table has been derived from it. To 
use, measure the height of the water column 
in feet, find from the table the factor for this 
height, and multiply the square root of the 
radiating surface in square feet by this fact- 
or. The result will be the size of the flow 
pipe, in inches (diameter) required. This 
is based on the assumption that there is a 
difference of lo degrees in temperature be- 
tween the water when it leaves and when it 
enters the boiler. 

Height of 
Column (ft.) Diameter Factor 

5 0.133 

10 0.113 

15 0.104 

20 0.095 

25 0.091 

30 0.187 

For example, to supply a coil of ten i5^- 
inch pipes loo feet long (500 square feet) 
15 feet above the bottom of the boiler, would 
require a feed pipe the diameter of which 
would be represented by V500 x 0.104 equals 
22.4 X 0.104 equals 2.33 or a 2%-inch pipe. 

Short Methods. — The above formula 
takes into consideration the fact that the 
greater the height of the column of water 
the more rapid the flow and consequently 


the smaller may be the supply pipe used. In 
greenhouse heating, however, the height is 
seldom very great, usually varying between 
8 and 20 feet, so that the following rule of 
thumb usually proves satisfactory. The flow 
pipe should be one pipe size greater in dia- 
meter (inches) than the square root of the 
radiating surface of the coil (in square feet), 
divided by 10. Applying this rule to the 

above problem we have Vsoo-^ 10=2.24 
The next pipe size is 2>^ inches but this is 
so close to the estimated size that a 2>4-inch 
pipe should be used to insure efficiency. 

The size of the main supply pipe from the 
heater is determined in the same manner by 
taking the sum of all the radiating surface 
to be supplied. It is better to have one main 
flow pipe leading from the boiler, from 
which branches to the various coils may be 
taken, than to have a flow pipe direct from 
the boiler for each coil, though two or more 
flow pipes may be taken oflF. The return 
pipes should be of the same size as the flow 
pipes. The flow pipe is taken from the top 
of the boiler and the return pipe enters at 
the bottom. 

In Fig. 94 is shown a diagram of a method 
for piping a medium-sized house. In the dia- 



Fig. 94. — A method of piping a medium size house 

gram A is the flow pipe extending directly 
up from the boiler; B, B, branch flow pipes; 
C, C, branch flow pipes extending the length 
of the house ; D, D, distributing pipes at the 
opposite end of the house; E, E, E, E, the re- 
turn coils; F, F, F, F, return pipes; and G, 
expansion tank. 

Valves should be conveniently placed so 
that any or all of the coils may be cut off in- 
dividually. They may be placed either in the 
flow or return pipe, or in both. If there is a 
valve in both the supply and return from each 
coil, any one may be repaired in case of an 
accident without drawing the fire or inter- 



Fig. 95. — Diagram showing under-bench method of hot 
water piping. A and B flow pipes; C and D heating coils 

fering with the circulation in the other coils. 
The valves should be of a type which, when 
open, cause as little resistance to the flow of 
water as possible. 

Length of Coils. — The length of the coils 
which may be used depends: (i) Upon the 
height of the column of water; (2) upon the 
size of the pipes which make up the coils; 
and (3) the amount of friction in the coils 
and fittings. The length of coils which may 
be satisfactorily used with pipes of various 
sizes are given in the following table. 


Size of pipe Length of coil 

1 inch Up to 50 feet 

Iji inch 50 to 75 feet 

1^ inch 75 to 100 feet 

2 inch 100 to 150 feet 

This table is based on the supposition that 
gravity, only, is to be depended upon for 
circulation. When pumps are used to cir- 

Fig. 96. — Gasoline engine arranged to circulate hot water 
in a greenhouse heating system 


culate the water the length may be materially 

The most commonly used size is i /4-inch, 
and when the houses are much over lOO feet 
in length two or more coils may be used, 
each extending only a part of the length, and 
having separate feed and return pipes. 

Expansion Tank. — Water expands in 
heating. It is necessary, therefore, to make 
some provision to take care of the expan- 
sion, in order that the pipes shall not burst 
and to keep them full at all temperatures. 
This is accomplished by connecting the sys- 
tem with an expansion tank into which the 
excess water will flow as it expands, and 
from which it will flow back into the system 
as it cools. It is placed at or above the high- 
est point in the system, but it may be con- 
nected with any part of the system or even 
with the boiler. 

The size of tank required is directly 
proportional to the volume of water con- 
tained in the system and is determined by 
the amount of expansion resulting from 
heating. The following table adapted from 
Kent shows the relative amount of expansion. 


Temperature Temperature Comparative 

Cent. Fahr. Volume 

4° 39. 1 ° 1 .00000 

10° 50. ° 1.00025 

20° 68. ° 1.00171 

30° 86. ° *. . . . 1.00425 

40° 104. ° 1.00767 

50° 122. ° 1.01186 

60° 140. ° 1.01678 

70° 158. ° 1.02241 

80° 176. ° 1.02872 

90° 194. ° 1.03570 

100° 212. ° 1.04332 

From the above table it will be seen that 
the increase in volume from 50 to 212 de- 

Fig. 97. — Automatic expansion tank. This is con- 
nected with the city water system and will auto- 
matically keep the heating system filled. See also 
G, Fig. 94 


grees is 1.04432 — 1.00025=0.04307, or a little 
more than 4 per cent. It is customary to 
make the expansion tank large enough to 
hold 5 per cent, or a twentieth of the water 
contained in the system, including the boil- 
er. Thus, if the system contains 100 gal- 
lons, the supply tank should be large enough 
to hold a twentieth of that amount or 5 

The capacity in gallons of a linear foot of 
standard wrought pipe is shown in the fol- 
lowing table. 

Size of pipe Capacity per 

diam. in inches linear foot 

1 0.1408 gallons 

UA 0.0638 

VA 0.0918 

2 0.1632 

2A 0.2550 " 

3 0.3672 

4 0.6528 " 

5 1.0200 

6 1.4690 

Pressure Systems. — Water in an open 
kettle cannot be heated above 212 degrees at 
sea level. At that temperature it boils and 
all further heat energy is expended in vapor- 
izing the water. In an open hot-water heat- 
ing system the same is true, except that the 


slight pressure of the column of water in the 
system may permit the water in the boiler to 
reach a temperature slightly above 212 de- 
grees. If water can be kept under pressure it 
may be raised to almost any desired tempera- 
ture, and in a heating system this would mean 
less necessary radiating surface. The boil- 
ing point of water under various pressures 
above normal or atmospheric pressures is 
shown in the following table: 

Pounds pressure Boiling point 

Normal 212.0° Fahr. 

V2 pound 2137° 

1 " 215.3° 

2 " 218.5° 

3 " 221.5° 

4 " ....224.4° 

5 " 227.1° 

6 " 229.7° 

10 " 240.0° 

Several systems have been evolved to pro- 
duce pressure in a heating system. One of 
the earliest was the closed tank system in 
which the expansion tank was made air-tight 
and fitted with a safety valve set so as to let 
the air in the tank escape at a certain pres- 
sure. By this means the water in the coils 
may be made to reach a temperature con- 
siderably above the boiling point. 



Recently various automatic devices using 
a column of mercury to produce the same re- 
sult have been placed on the market. One 
model is designed to be placed in the pipe 
leading from the return pipe to the expansion 
tank, the tank in this case being open. The 
advantage of these devices over the closed 
tank system lies in the fact that they are 
less likely to become clogged and stick than 
are the safety or pop valves. 

In action these so-called 
"generators" operate as 
follows: The pressure is 
determined by the height 
of the column of mercury. 
When there is no heat in 
the boiler the mercury is 
in the position shown at a, 
Fig. 98. As soon as the 
water becomes warm it ex- 
pands and flows in through 
the opening x. This forces 
the mercury down in the 
cistern and up through the 
small pipe b. The amount 
of mercury is so arranged 
that when it is pushed 
down to the level of the 

Figr. 98.— A type 
of mercury "gen- 


curve in the outlet pipe at c it overflows at d. 
This allows some of the water to escape, and 
this goes up through the pipe e to the ex- 
pansion tank, but the mercury being heavier 
falls back again through f to the cistern. 

This automatically keeps the pressure at 
any predetermined point, usually about lo 
pounds, which makes possible the heating of 
the water to a temperature of 240 degrees. 
This makes practical the heating of the coils 
to a high temperature in severe winter 
weather and at the same time permits the 
system to be run at lower temperatures in 
mild weather. In this respect it has the ad- 
vantage over steam. It is claimed for these 
mercury "generator" devices that they 
greatly improve the circulation of the water 
in a heating system. 

The most apparent advantage is that they 
make possible the use of less radiating sur- 
face, hence the first cost is less. It is but 
fair to say that, as a rule, growers who have 
installed them have found them satisfactory. 
When the hot water is circulated by 
pumps it IS possible, though probably not de- 
sirable to maintain a high pressure. Econ- 
omy in heating by hot water lies in having 
abundant radiating surface and rapid circu- 


lation and then keeping the water at a mod- 
erate temperature. 

Caution. — In any system see that the ex- 
pansion tank and the pipe leading to it are 
placed where they will not freeze. As there 
is ordinarily no circulation in the water they 
contain they will freeze if placed where the 
temperature falls below freezing. The re- 
sults will almost surely be disastrous. 


General Principles. — In steam heating 
there is no circulation in the same sense that 
there is in hot water heating, but the steam 
is conducted into the heating coils^ where it 
condenses. In condensing it gives up its 
"latent'' heat. The water of condensation, 
which occupies only about 0.017 part of the 
space occupied by the steam, finds its way 
back to the boiler either by flowing back 
through the supply pipes, or through return 
pipes connected with the opposite ends of the 
coils. The latter system is most commonly 
used in greenhouse heating. 

In contrasting steam and hot-water heat- 
ing it is well to keep in mind the fact that 
only 180 B. T. U. are required to raise one 

♦In order to avoid repetitiom steam heating is- discussed 
largely in contrast to hot water heating, as described 
in the preceding chapter. Both chapters should be 
read by one wishing to inform himself on steam 



pound of water from 32 to 212 degrees but 
that 966 B. T. U. (usually considered as icxx)) 
are required to change a pound of water at 
212 degrees into steam. When the steam is 
condensed in the coils it gives off this heat. 
This is known as the latent heat of steam. It 
may be defined as the amount of heat ab- 
sorbed in changing from a liquid to a vapor 
or the amount given off in changing from a 
vapor to a liquid state. 

The problem in steam heating is to supply 
an amount of radiating surface sufficient to 
condense enough steam to furnish the 
amount of heat required. Under ordinary 
greenhouse conditions a square foot of steam 
radiating surface may be counted on to con- 
dense approximately one quarter pound of 
steam per. hour. Each square foot of radi- 
ating surface will, therefore, provide a fourth 
of 960 or approximately 240 B. T. U. per 

The number of B. T. U. required per hour 
to heat a given house (see page 172), divided 
by 240 will give, therefore, the number of 
square feet of steam radiation required, and 
from the table on page 174 the number of 
linear feet of pipe may be easily determined. 
Assuming a steam pressure of five pounds 


per square inch the following rule will be 
found useful in determining the amount of 
steam radiation required for a house when 
the lowest outside temperature to be ex- 
pected is not lower than zero. 

Divide the numter of square feet of glass 
and equivalent glass. 

By 9 to heat house to 40 degrees 
By 7 to heat house to 50 degrees 
By 6 to heal house to 60 degrees 
By 5 to heat house to 70 degrees 
The quotient will be the number ol square feet of 
radiating surface required 

Size and Length of Coils. — There is less 
friction in steam than in hot-water heating, 
and for this reason smaller pipes may be used 
in the heating coils. They are seldom larger 
than 1%-inch, and i%-inch is very commonly 
used. Even i-inch pipe may be used in 
comparatively short runs. Smaller pipes 
may also be used in steam than in hot-water 
heating, for the r^eason that the radiation per 
square foot of surface is greater and there- 
fore less surface is required. In other words, 
an equal number of smaller pipes or a small- 
er number of pipes of equal size may be used 
in steam than in hot-water heating. Small 
pipes furnish a greater amount of radiation 
in comparison to their cubic capacity than 



do large pipes. Large cast-iron pipes are 
almost never used in steam heating. 

When i-inch pipe is employed coils may be 
safely used up to 75 feet in length; VA- 
inch up to 150 feet; and i>^-inch up to 250 
feet. As with hot water, better results and a 
more uniform temperature may be secured 
by using two or more comparatively short 
coils, rather than one which is excessively 
long. In small houses it is possible to run 
the coils entirely around the house, maintain- 
ing an even downward slope. 

Arrangement of Coils. — ^As indicated in a 
preceding paragraph, either of two methods 
of piping may be used. In one the water 
resulting from the condensation of the steam 

Fig. 99.— A corner coil. It allows for expansion of the 



flows back to the boiler through the supply 
pipe. In this case all pipes have an upward 
slope from the boiler, with no sags or pock- 
ets in which the water can collect. This 
method, sometimes known as the single pipe 
system, is very commonly used in heating 
dwellings where the pipes are mostly verti- 


Fig. 100. — A mortise coil designed to allow for expan- 
sion of pipes 

cal, but in greenhouses having long, nearly 
horizontal coils there is likely to be much 
hammering in the pipes, caused by the in- 
terference of the steam with the return 

A more satisfactory method for green- 
house heating is to arrange the pipes much 
the same as in hot-water heating, pro- 
portioning the size to the supply and re- 


turn pipes according to directions given in 
a following paragraph. This is known as 
the two-pipe system. The return pipe en- 
ters the boiler below the surface of the water. 
The coils should have a fall toward the boiler 
of' about I inch to 20 feet. It is not wise 
to use the straight coils commonly used for 
hot water in steam heating as they do not 
allow for the unequal expansion of the pipes 
when the steam is turned on quickly. In 
steam heating special form of coils are com- 
monly used among which are the corner coil 
and mortise coil. 

Size of Supply and Return Pipes. — Theo- 
retically, the size of the flow and return pipes 
in steam heating may be much smaller than 
in hot-water heating. This is especially true 
of the return pipe, since the water which it 
carries occupies only 0.017 of the space oc- 
cupied by the steam from which it is con- 
densed. In practice, however, the flow or 
supply pipe for steam is made nearly as large 
as for hot water and the return pipe only 
slightly smaller. 

The following table shows the flow of 
steam in pipes of different sizes at a pressure 
at the boiler of approximately five pounds. 


Size of 


V/i inches 



















Pounds of steam per hour 











To find the size of supply pipe required it is 
only necessary to determine the number of 
pounds of steam condensed per hour by the 
coils (approximately one-quarter pound for 
every square foot of radiation) and from the 
above table select the correct size. 

The following table, adapted from Carpen- 
ter, gives the size of supply and return pipes 
recommended to be used in the two-pipe sys- 
tem for different amounts of radiation, 
when a pressure of not greater than five 
pounds IS used. 

Sq. ft. of radiation 
to be supplied Size of supply pipe Size return pipe 

200 VA inch 1% inch 

400 2 " VA 

700 2y2 " .....2 

1000 3 " 2 

1600 ^A " 2A 

2300 4 " 2A 

3200 A-A " 2A 















Valves. — In steam heating it is essential 
that each coil be provided with a cut-oflf 
valve. This is even more essential than with 

Fig. 101. — Reducing valve 


hot water since with steam heating the tem- 
perature of the steam must be at least 212 
degrees, while with hot water the tempera- 
ture may be varied according to the weather. 
Automatic air valves are placed at the high- 
est point of each coil and also in the supply 

High Pressure Heating. — When steam 
above five pounds pressure is used it is known 
as high pressure heating. For greenhouse 
purposes high pressure heating is not satis- 
factory, as the pipes are too hot. In 
large establishments, however, a high press- 
ure is often maintained at the boiler and is 
passed through a reducing valve before it 
enters the coils. 

Vacuum and Vapor Systems. — Several 
heating systems are now on the market which 
endeavor to give to steam heating some of 
the advantages claimed for hot water, viz., a 
lower temperature of the heating pipes and 
less frequent attention to the boiler. They 
differ from straight steam heating in that a 
partial vacuum is maintained within the 
system, thus causing the water in the boiler 
to give off vapor at a temperature of less 
than 212 degrees. 


There are several different systems but 
they may all be grouped roughly into three 
classes: (i) Those in which a vacuum is 
created by means of a pump or other me- 
chanical device; (2) those in which the air 
is expelled by raising the steam to a relative- 
ly high pressure, and then preventing it from 
returning by some form of automatic mer- 
cury seal, and (3) those in which a constant, 
though slight, vacuum or tendency to vac- 
uum is maintained, by connecting the sys- 
tem with the chimney and utilizing the "pull'' 
of the draft. 

These systems are now being rapidly in- 
stalled in public buildings and dwellings, and 
no doubt will be found more satisfactory 
than steam for greenhouses. In addition to 
the advantages given above it is claimed for 
these systems that they are more economical 
of fuel than are either steam or hot water, 
that the circulation is better and surer, and 
also that there is no trouble arising in long 
runs from water of condensation. 

Arrangement of Boilers. — In the common 
gravity system of steam heating the boilers 
must be below the level of all mains and 
coils. When they cannot be so located, 


special devices to be described later must 
be employed to return the water of conden- 
sation. As with hot water, two or more 
boilers should be provided, rather than one 
large one, to allow for repairs in case of ac- 
cident and for use in severe weather to avoid 
the necessity of forcing. 

Steam Pumps and Traps. — As suggested 
in the preceding paragraph, it is sometimes 
impossible or inconvenient ta place the boil- 
er below the level of the heating coils. This 
is especially true in large establishments, re- 
quiring large boilers using large quantities 
of fuel. In order to return the water of con- 
densation in such cases steam return traps 
and steam pumps are used. Their use is al- 
so necessary where a higher pressure is car- 
ried at the boiler than in the coils. 

The return trap is a contrivance which is 
automatic in its action, and which overcomes 
the back pressure from the boiler by an in- 
genious method of equalizing the difference 
in pressure between the boiler and the coils. 
Being automatic in its action and requiring 
but little attention it has been quite gener- 
ally used. Steam pumps, on the other hand, 
require considerable attention, though they 


are less complicated than the return traps. 
A small, separate boiler is generally used to 
operate the pump, and the exhaust and sur- 
plus steam is turned into the general heat- 
ing system after being reduced to low pres- 
sure. Gas and electric motors are also used 
to drive the pumps for returning the water 
of condensation. 

Fig. 102. — A type of steam return trap 


The terms boiler and heater as used in dis- 
cussing greenhouse heating systems are 
synonymous. It is customary, however, to 
speak of a steam heating apparatus as a 
**boiler" and of a hot-water heating appar- 
atus as a "heater," probably because in steam 
heating the water boils, while in hot-water 
heating it is not supposed to boil. It often 
occurs, however, that the same kind of heat- 
ing apparatus is used in both steam and hot- 
water heating with no essential changes, ex- 
cept in the accessories. In this chapter the 
term boiler will be applied to both steam and 
hot-water heating devices. 

The boilers used in greenhouse heating 
differ but little from those used in heating 
other buildings. In fact the same makes 
and styles of boilers are very frequently used 
for both purposes. Certain manufacturers 
have, however, made a thorough study of 
greenhouse heating and have developed boil- 



ers with this particular end in view. In 
buying a boiler the safe plan is to purchase 
a style which has fully established itself on 
the market and which is made by a thorough- 
ly reliable firm. Such boilers will have passed 
the experimental stage and repairs may be 
secured quickly and reasonably. 

Essentials of a Boiler. — The function of 
the boiler is to extract the latent heat from 
the fuel and transfer it to the water or steam, 
which may be circulated when needed. The 
essentials are, a grate on which the fuel is 
burned and a watertight receptacle, so ar- 
ranged as to present a large amount of sur- 
face (known as fire surface) to the fire or 
burning gases. The problem of the manu- 
facturer is to so arrange and proportion the 
fire surface and the grate surface that the 
heat of the burning fuel may be most econ- 
omically absorbed and distributed. 

Grate Surface. — For best results the 
amount of grate surface should be large 
enough, so that the fire will not have to be 
forced. In small and medium-size boilers 
the rate of combustion should not exceed 
from five to seven pounds of coal per square 
foot of grate per hour. In larger boilers the 
rate of combustion of fuel may be as high as 


from six to ten pounds per square foot per 

A pound of best coal has a heating value 
of about 14,000 B. T. U. per pound, of which 
only about 60 per cent, or 8,400 B. T. U. are 
utilized in heating w^ter or producing 
steam. It is the usual practice to estimate 
that each pound of coal will impart about 
8,000 B. T. U. to the heating medium, and 
that each square foot of grate surface will 
burn about six pounds of coal per hour. This 
gives 48,000 B. T. U. per square foot of grate 
surface per hour. 

To find the approximate number of square 
feet of grate surface required to heat a given 
house, find the number of heat units re- 
quired, by the method described in Chapter 
XI, and divide by 48,000. 

In general, a square foot of grate surface 
is sufficient to supply 250 square feet of 
radiating surface. 

Fire Surface. — Fire surface (sometimes 
known as heating surface or water surface) 
is of two kinds; direct and indirect. The 
direct fire surface is that immediately above 
or around the fire, against which the light 
of the burning fuel shines. Indirect fire sur- 
face IS that which receives the heat from the 


burning gases on their way to the chimnevc 
Direct fire surface is three times as effective 
as indirect. It does not follow, however, 
that boilers having the greatest amount of 
direct fire surface are the most efficient, for 
there must be sufficient length of fire travel 
to consume the gases and enable them to give 
up the greater part of the heat of combus- 
tion to the water. 

To be most effective the fire surface is so 
arranged that the heat will impinge at right 
angles against it. This is accomplished with- 
out serious interference with the draft, 
and without making the course of the water 
in the boiler so long and tortuous as to in- 
terfere with its rapid circulation. The pro- 
portion of fire surface to grate surface dif- 
fers so widely in the different forms of boil- 
er construction that no definite rule can be 
given. It may vary from 15 to 35 square 
feet to each square foot of grate area. 

Types of Boilers. — Broadly speaking, 
there are three types of boilers, when classi- 
fied as to their form of construction : ( i ) Boil- 
ers in which the water is spread out in thin 
sheets between layers of iron or steel and 
against which the heat strikes; (2) tubular 



boilers in which the burning gases travel 
through tubes or flues which are surrounded 
by water; and (3) water-tube boilers in 
which the water is contained in tubes about 
which the burning gases circulate. Many 

Fig. 103. — A type of "vertical ' or 
"square" sectional boiler 

manufacturers combine two, and sometimes 
all, of the above types in one boiler. The 
two latter types are more commonly used 
for power purposes than is the first, but for 
heating establishments of moderate size a 
modification of the first is widely used. 



Cast and Wrought-Iron Boilers.--rThe 

cast-iron boiler has a size limit above which 
it is impracticable to go, though two or more 
may be joined in a series. It is also claimed 
that on account of the thickness of the walls 

Fig. 104. — End view of "square" sectional 

boiler showing fire travel. A and B, push 

nipples for joining sections 

it is less economical of fuel than are wrought- 
iron boilers, which have thinner walls. On 
the other hand, cast-iron boilers do not rust 
as badly as wrought-iron ones when not in 
use, and they have no flues to be burned out 
by the sulphurous gases resulting from the 



use of the poorer grades of coal. But they do 
sometimes crack, and they have a disgusting 
way of doing it at the most inopportune 

Fig. 105. — Side view of **square" sectional boiler 
showing fire travel 

Where fuel is cheap and abundant, and 
especially in small ranges, or where the boiler 
is in a damp basement and likely to be neg- 
lected during the summer, cast-iron boilers 
are likely to give better satisfaction than 
wrought-iron. In large establishments ^of 
100,000 feet or over, large wrought-iron tubu- 





lar or water-tube boilers are almost always 

Styles of Cast-iron Boilers. — There are 
three general types or styles of cast-iron 
boilers. The most popular is the "vertical" or 

"square"sectional boil- 
er. The advantages 
claimed for these forms 
of boilers are: (i) 
They may be enlarged 
by adding extra sec- 
tions; (2) a break or 
crack will usually be 
confined to one sec- 
tion ; and (3) they may 
be made in large sizes 
because the individual 
castings are compara- 
tively small and light. 
The sections are joined 
together by accurate- 
ly ground push nip- 
ples or by screw nipples. Probably 80 per 
cent, of the cast-iron boilers now beinsr 
placed in greenhouses of moderate size are 
of this general type- 

A second style of cast-iron boiler is 
known as "horizontal" or "round" sectional 
boiler. It gives good satisfaction in small 

Fig. 107.— A type of 

' round" or "horizontal" 

sectional boiler 



ranges but is not made in large sizes. In 
a third style there are no sections, but the 
boiler proper is cast in one piece. For this 
reason its size is limited. It is also open 
to the disadvantage that a crack will spoil 
the whole boiler. It is little used at present. 

108. — Corrugated fire box •boiler. The boiler 
proper is of a single casting 

Styles of Wrought-Iron Boilers. — Most 
wrought-iron boilers are either tubular or 
water-tube in construction, though the tubes 
or flues are sometimes connected with cast- 
iron headers. A new type of wrought-iron 
boiler is now being extensively advertised for 
greenhouse heating. It is claimed for this 
type that it steams more quickly than the 



i'ig. 109. — Type of tubular boiler much used in green- 
house heating 

tubular boilers and that it is much more dur- 
able. As a rule users seem to be well satis- 
fied with it. 

Steam and Hot-water Boilers. — As usually 
constructed, low-pressure steam boilers dif- 
fer but little in construction from hot water 
boilers. The essential difference is that in 
steam boilers provision is made for a steam 
chest or storage above the water line, while 
in hot-water boilers the space between the 
top of the tubes and the top of the boiler is 
so small that there is no room for an adequate 
steam storage. This is equivalent to saying 


Fig. 110. — Battery of two marine type boilers used for 
greenhouse heating 

that a steam boiler may be used for hot-water 
heating, but that a hot-water boiler is rare- 
ly satisfactory for steam heating. Large 
steam boilers are quite frequently used in 
hot-water heating when equipped with the 
necessary fittings which are described in 
a succeeding paragraph. 

Boilers for Soft and Hard Coal. — Hard coal 
burns with a ''short" flame, and much less 
fire travel is required to burn the gases than 
when soft coal, which burns with a "long" 
flame, is used. More flue way is also re- 
quired for soft coal and the grates are more 
open. Most greenhouse boilers which are 



designed for soft coal will burn hard coal 
equally well. If they are designed primarily 
for hard coal they will not burn soft coal 
efficiently. More grate surface is required 
for soft coal than for hard coal, because it is 

Fig. 111. — Wrought-iron boiler without flues 

more bulky weight for weight. Most mod- 
ern greenhouse boilers will burn either hard 
or soft coal, but a larger size will be required 
for soft coal than for anthracite. 

Boiler Ratings. — An approximate idea of 
the size of boiler needed may be found by 
figuring the amount of grate surface by the 
method described on page 202. Boiler manu- 


facturers, howev,er, rate their boilers show- 
ing their capacity. Some give the number 
of square feet of glass that they will heat to 
a given temperature ; others give the number 

Fig. 112. — Sectional view of boiler shown in Fig. Ill 

of linear feet of radiating pipe of a given 
size which they will supply ; and still others, 
especially the manufacturers of large tubu- 
lar boilers, give the capacity of their boilers 
in terms of horse-power. 

Since different manufacturers often ques- 
tion the correctness of the ratings of their 


competitors, it is but fair that buyers 
should be recommended to exercise consider- 
able caution. Probably most boilers will, 
under favorable conditions, develop the num- 
ber of heat units for which they are rated, 
but for the sake of safety and to prevent the 
necessity of forcing, it is best to select boil- 
ers with ratings at least 20 per cent, in ex- 
cess of the theoretical needs. 

When boilers are rated according to the 
number of linear feet of radiating pipe they 
will supply, it is usually given in terms of 
either 3%-inch cast-iron pipe or in 2-inch 
wrought-iron pipe. The following table 
gives the length of pipes of other sizes equiv- 
alent to I linear foot of 2 and 3V^-inch pipe. 

1 ft. of 5^ in. C.I.- pipe equals.. 3.04 ft. 1 
1 ft. of 3^ in. C.I. pipe equals.. 2.41 ft. 1^4 
1 ft. of 3-^ in. C.I. pipe equals.. 2.10 ft. IH 
1 ft. of 3^ in. C.I. pipe equals.. 1.68 ft. 2 
1 ft. of 3-^ in. CI. pipe equals. .1.39 ft. 2^ 
1 ft. of 2 in. W.I. pipe equals.. 1.806 ft. 1 
1 ft. of 2 in. W.I. pipe equalsf. .1.431 ft. 1J4 
1 ft. of 2 in. W.I. pipe equals. .1.25 ft. VA 

in. W.I. pipe 

n, W.I. pipe 

n. W.I. pipe 

n. W.I. pipe 

n. W.I. pipe 

n. W.I. pipe 

n. W.I. pipe 

n. W.I. pipe 

Most boiler ratings are given for a mini- 
mum outside temperature of zero degrees, 
Fahrenheit. For localities subject to a tem- 
perature of lo degrees below zero a boiler 
of lo per cent, greater capacity should be se- 



cured, and for localities subject to a tem- 
perature of 20 degrees below zero, a boiler of 
20 per cent, greater capacity should be se- 

The term horse-power, as applied to boil- 
ers, represents the energy developed in evap- 
orating 34.5 pounds of water per hour from 
a. temperature of 212 degrees, or the develop- 
ment of 33,317 B. T. U. per hour. Roughly, 
a heating boiler will supply 100 square feet 
of radiation for each horse-power which it 

Fig. 113. — Altitude guage for hot 
water boiler 

Boiler Accessories. — It has already been 
stated that a steam boiler may be used for 
hot-water heating by simply changing the 
fittings. When used for hot-water heating 



the boiler is fitted with an altitude gauge, 
which shows the height of the water in the 
system ; also with a thermometer to show the 
temperature of the water. A valve is pro- 
vided for draining the boiler and, if desired, 
an automatic damper regulating device may 
be installed. 

When used for steam 
heating the boiler is only 
partially filled with water, 
and a water column and 
guage is necessary to indi- 
cate the height of the 
water. A steam guage is 
also necessary to indicate 
.the pressure; and a safety 
valve to automatically re- 
lieve the pressure, if it be- 
comes too great for safety. 
Steam boilers are usually 

Fig. 114.— Water col- . , . . ^ ^f 

umn and guage for equipped With automatic 
steam boilers hamper regulators. They 
are rather more efficient than the regulators 
used on hot-water boilers. A drainage valve 
is provided the same as for hot-water boil- 
ers. Many states require that all steam boil- 
ers be equipped with a fusible plug, which is 
simply a brass plug with a tin core, which 


, Fig. 115. — Steam guage 

is screwed into a hole in the boiler near 
the bottom. If the water level falls below 
the plug the heat melts it out, thus making 

Fig. 116. — Diagram of automatic damper regulator. The 

steam pressure acts against a flexible diaphram which 

is connected with the dampers by means of a lever and 



an opening and lessening the danger of an 

The boiler and all pipes, except those in 
the greenhouse itself, should be insulated as 
much as possible to prevent loss of heat. The 
best known material for this purpose is as- 
bestos. For coating boilers it may be had 
in a granular form, which is mixed with 
water and applied with a trowel or the bare 
hands. For covering pipes molded casings 
may be had to fit all sizes of pipe. 

Fig, 117. — Asbestos pipe covering 

Coal is used almost universally for fuel in 
greenhouse heating, except in sections where 
natural gas or oil are cheap and abundant. 
Gas is an ideal fuel, but somewhat treach- 
erous inasmuch as the pressure is likely to be 
lowest in the coldest weather. Care should 
be taken to see that there are no leaks, as it 
is very explosive, and it is also poisonous to 
vegetable as well as animal life. 

Broadly speaking, coal is of two kinds, 


anthracite or hard coal, and bituminous or 
soft coal. Hard coal burns with little smoke 

Fig. 118. — Boiler equipped for using natural gas 

and is much heavier than soft coal, although 
it may not develop as much heat per ton. 


It IS easier and cleaner to handle, and re- 
quires less attention in firing, but in most 
sections is more expensive. 

Soft coals are of two general types; The 
free burning and the coking. The latter 
fuses together in burning and is somewhat 
more difficult to handle in the furnace than 
the free burning, though it is preferred by- 
some firemen. 

The heating value of a coal depends upon 
the percentage of total combustible matter 
contained, and upon the heating value per 
pound of the combustible portion. In some 
semi-bituminous coals the heating value runs 
as high as 15,750 B. T. U. per pound. The 
heating value of a few common types of 
coals as given by Kent are shown in the fol- 
lowing table. 

Kind of coal B.T.U. Kind of coal B.T.U. 

Anthracite Cambria Co., Pa. . . . 14450 

Northern Coal field ..13160 Somerset Co., Pa. ...14200 

East Middle field ...13420 Cumberland, Md 14400 

West Middle field ...12840 Pocahontas, Va 15070 

Southern field 13220 Brier Hill, 13010 

Scott Co., Tenn 13700 

SemiJbituminous Big Muddy, III 12420 

Clearfield Co., Pa. ...14950 Missouri 12230 

Soft coal is more commonly used in green- 
houses than is hard coal. This js especially 


true in large establishments. The price 
varies with the quality, distance from the 
mines, etc. 

The average cost for soft coal to 6i grow- 
ers, living east of the Mississippi River, for 
the season of 1911-12, was $2.33 per ton. The 
average amount used for the season was 11.6 
tons for each 1,000 square feet under glass. 

Underfed Boilers. — ^The term "underfed'' 
is applied to a method of stoking, in which 
the coal is fed from the bottom instead of 
the top of the furnace. It is claimed for 
this system that it insures a more perfect 
combustion and that cheaper grades of coal 
may be used. Boilers employing this prin- 
ciple have not come into very general use in 
greenhouse heating, probably because they 
will not handle successfully all grades of 

Self-stoking Boilers. — Stoking devices are 
practical only in large establishments us- 
ing large boilers. There are several types, 
some of which work on practically the same 
principle as the underfed furnaces mentioned 
above, except that their action is automatic. 
In other forms the grate bars are arranged 
in the form of an endless chain, which is 


moved slowly from the front to the rear 
of the fire-box by means of gearing. It is 
claimed for the self-stoking devices that they 
not only save labor, but that they are more 
economical in the use of fuel than is hand 

Points to Consider. — The following points 
should be kept in mind in selecting a green- 
house heating boiler: 

1. It should be of ample size — at least one 
size larger than is theoretically necessary. 

2. The fire-box should be deep and spac- 
ious. This is especially true of boilers for 
small establishments where a regular fire- 
man is not employed. 

3. The combustion chamber (the chamber 
above the grate) should be large enough to 
insure thorough combustion of the gases. 

4. The boiler should be so arranged that 
it may be easily cleaned, especially the flues 
and heating surfaces. 

5. The grates should be heavy but easy 
to operate and easily removable, so that re- 
pairs may be made quickly. 

6. The water travel should not be so cir- 
cuitous as to prevent of rapid circulation. 

7. There should be no packed joints. All 


unions should be made with push or screw 

8. Soft coal burners require a somewhat 
different construction than do hard coal burn- 
ers. The kind of fuel to be burned should 
be clearly in mind when selecting a boiler. 

9. The ash pit should be deep and com- 
modious. Shallow ash pits are likely to be- 
come filled so that the draft is impaired 
and the grate bars ruined. 

A very essential part. of the heating equip- 
ment is the chimney or flue. Its purpose is 
twofold: First, to create a draft in order 
to furnish air to promote combustion; and 
second, to carry off smoke and gas. The 
size and height of the chimney required de- 
pends on the size of the grate surface. Mere 
velocity does not necessarily indicate that 
the draft is sufficient; the chimney must be 
of sufficient size to carry the required 

The velocity of the gas in the flue depends 
on the height of the flue and upon the tem- 
perature of the gas. The difference be- 
tween the weight of the hot gases in the 
chimney, and a column of cold air of equal 



size outside creates a flow upward in the 
chimney. This difference increases with the 
height of the chimney, and if the difference 
in temperature increases the velocity is more 
rapid. Locations high above sea level require 
higher chimneys than those near sea level, 
on account of the rarety of the atmo- 

Fig. 119. — Chimneys should extend above the roofs of 
adjacent buildings 

sphere. For example, at Denver, Col., (5,300 
feet) the height should be about 20 per cent, 
greater than at sea level. 

Chimneys should be vertical if possible and 
the inside should be smooth and free from all 
obstructions. They should also extend well 
above the roofs of adjacent buildings, particu- 
larly when there is danger of a "down 
draft." Round chimneys present less sur- 
face per cubic capacity than do square chim- 
neys, and are thus more efficient. For the 
same reason square flues are better than ob- 
long flues. 


The following table shows the size and 
height of chimneys required by steam boil- 
ers. For hot-water boilers multiply the radi- 
ating surface by 1.5. 

Height of chimney in feet 

Sq. ft. 









st'm rad 

Size of Chimney (dia. 

or 1 sid 

e sq.) 

in inches 

































































































































• • . 








• . • 

• • • 










.. . 







An abundant supply of water at a reason- 
able cost is necessary for the successful op- 
eration of a commercial range of green- 
houses. Figures compiled from the experi- 
ence of several growers show that the con- 
sumption of water by a vegetable crop in a 
greenhouse during the bright,, hot days of 
June and July may be as high as 280 gallons 
per day per 1000 square feet of crops. As 
the watering is done over a period of not 
more than three or four hours per day, it is 
necessary to make arrangements to supply 
the maximum amount needed during that 
length of iime, rather than during the 24 
hours of the day as is usually figured for 
domestic purposes. 

When city water is available at a reason- 
able price it is doubtful if it will pay the 
small grower to go to the expense of pro- 
viding a private supply. Sometimes, how- 
ever, the conditions are such that a private 




supply of water may be had at small expense 
from springs, ponds or streams. In larger 
establishments it may be cheaper to install a 
private system than to depend on city water. 
Often, also, the ranges are located out- 
side the city limits where city water can- 
not be had. Data based on the reports of 

nearly lOO florists and 
vegetable growers 
show that the average 
cost per I, GOO gallons 
of city water is i8 
cents, and that the 
average cost of the 
home supply, includ- 
ing cost of equipment, 
depreciation and main- 
tenance, is 21 cents 
per i,ooo gallons. 

Pumps. — For gen- 
eral purposes some of 
the many types of 
combination lift and 
force pumps now on 
the market are com- 
monly used. Pumps 
of this type may be had which are directly 
geared to a gas or steam engine, or to an 

-Pumping jack 
for applying power to a 
hand pump 





ir-WSU. CAStAfa 

electric motor. Usually, a hand pump of 
large size is used, and power is applied by 
means of a pumping jack. 

A very efficient but somewhat delicate 
pumping device is the combined hot-air- 
engine and pump. 
These pumps give 
very good satisfac- 
tion where the water 
is reasonably close 
to the surface, or 
when it does not 
have to be pumped 
against too great a 
pressure. Improved 
types of large size 
are now available, 
and are very econ- 
omical of fuel, but 
the engine is not as 
well adapted for 
general power pur- 
poses as are gas en- 

A form of pump, which is becoming quite 
popular for domestic use is the auto-pneu- 
matic pump. It is designed to be used in 
an open well or a cased well of large bore, 
as the pump proper is placed entirely be- 


\</rO -PN£UMATfe 

Fig. 121. — Diagram showing 
installation of an auto- 
pneumatic pump 


neath the water. It is operated by com- 
pressed air, hence an air pump and an air 
tank are required. Its chief advantage for 
domestic purposes lies in the fact that it 
starts automatically when the faucet is 
opened, thus giving a supply of cold water 
direct from the well. For greenhouse pur- 
poses this is a disadvantage, as the water may 
be too cold to use on the plants. 

Pump cylinders should not be more than 
20 feet above the surface of the water, as this 
is the limit of practical suction. When the 
water is more than 20 feet below the surface 
the pumping cylinders are lowered accord- 
ingly. In deep wells it is common to lower 
the pumping cylinders well into the water. 

Capacity of Pumps. — The capacity of a 
pump depends upon the size of the cylinder 
and the length and rapidity of the strokes. 
The table on page 230 gives the discharge per 
stroke in gallons, of pumps having cylinders 
of various sizes. This, multiplied by the 
number of strokes per minute, will give the 
capacity per minute. 

Power Required. — The power required to 
operate a given pump may be determined as 
follows: Multiply the number of gallons 
pumped per minute by 8.357 pounds (the 




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weight of a gallon of water). This will give 
the weight pumped per minute. Multiply 
this by the total lift in feet. This will give 
the number of foot-pounds of energy nsquired 
per minute. Divide this by 33,000 (the num- 
ber of foot-pounds in a horse-power) and the 
result will be the numbec of horse-power re- 
quired. Pumping outfits are only about 50 
per cent, efficient, so that the results ob- 
tained by the above are doubled in actual 
practice. On the average one horse-power 
will pump 30 gallons per minute to the height 
of 100 feet. In pumping water against press- 
ure in a pneumatic tank, extra power will 
be required. Extra power will also be re- 
quired when the waten is pumped for any 
considerable distance, on account of the fric- 
tion of the pipes. The frictional loss in feet 
of lift for each 100 feet of pipe of various 
sizes is shown in the following table. 


Size of Pipe 

er min. 



154 in. VAixi. 

2 in. 


Frictional Loss 




1.4 1.0 






5.5 2.2 






9.5 4.8 






14.7 6.0 






21.0 8.6 






2S.9 11.6 



40 461.0 110.0 37.0 14.9 3.7 1.2 



This loss by friction cannot be disregarded. 
Suppose, for example, it is desired to deliver 
20 gallons per minute at a distance of 100 
feet. By referring to the above table it will 
be seen that if a ^4-inch pipe were used, a 
loss equal to a head of 115 feet would be 
sustained, while if a i%-inch pipe were used 
a loss of only 4.8 feet would be sustained. 
It is economy to use pipe of generous size. 

Hydraulic Rams. — The hydraulic ram is 
a device which utilizes the force of water. 

Fig. 122. — A simple type of hydraulic ram. a, intake 
pipe; f, delivery pipe 


falling a short distance, to elevate a portion 
of the water to a greater height. It is 
wasteful of water, but when a never-failing 
stream of sufficient flow and fall is avail- 
able it is one of the most economical and 
satisfactory of water-lifting machines. 

Rams are somewhat difficult to install by 
a novice, because of the rather exacting con- 

Fig. 123. — Plan for installing a hydraulic ram 

ditions necessary to secure the most efficient 
service. When they are properly installed, 
however, they give little trouble, provided 
they are kept from freezing. 

Capacity of Rams. — To find the capacity 
of a ram for any given conditions proceed as 
follows : Multiply the fall in feet by the quan- 
tity of water which may be supplied to the 
ram in gallons per minute, and divide the 
product by the height the water is to be 
raised. The result will be the number of 
gallons delivered per minute. The above 


disregards loss by friction and assumes that a 
ram of the proper size is installed. 

By use of the table on page 235 an estimate 
of the capacity of a ram for different con- 
ditions may be determined. The left-hand 
column indicates the number of feet of fall 
possible to secure, and the numbers at the top 
of the vertical columns indicate the height 
to which water is to be raised. 

For example: Suppose we have a stream 
with a flow of 100 gallons per minute; that 
there is an available fall of 10 feet, and that 
it is desired to raise the water 40 feet. The 
factor in this case (252) will be found in the 
column headed by 40 and opposite the num- 
ber 10 under power head. Multiplying 252 
by 100, we have 25,200, the number of gal- 
lons that may be delivered per day by a ram 
of the correct size. 

In ordering a hydraulic ram the following 
information should be given: 

1. Flow of water in gallons per minute. 

2. Vertical fall in feet. 

3. Distance in which fall is obtained. 

4. Vertical height above ram the water 
is to be raised. 

5. Distance water is to be forced. 

6. Number of gallons required per day. 





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To use: Multiply the factor opposite power head and under 
pumping head by the number of gallons of water avail- 
able per minute. The product will be the number of 
gallons delivered per day. (See page 234.) 


Double-acting rams which will utilize the 
water from a creek or river as power and 
pump water from a spring or shallow well 
may be had, but they are somewhat more 

Windmills for Pumping. — The chief ob- 
jection to the windmill for pumping is its lack 
of dependability. Where the wind is fairly 
constant, or when a large storage capacity 
may be had cheaply, windmills are the cheap- 
est source of power. On the average the 
windmills used for pumping develop about 
three-fourths horse-power. The geared steel 
wheel mills are more efficient and will run 
in lighter winds than will the wood wheel 

Storage Tanks. — Storage tanks are neces- 
sary with most water systems, to insure a 
constant supply and to furnish pressure. 
They fall naturally under two heads: (i) 
Open tanks in which pressure is obtained by 
gravity; (2) closed tanks, usually pneumatic 
tanks, containing air into which water is 
forced, the compressed air in this case furn- 
ishing the desired pressure. 

In placing tanks in the attic, or other ele- 
vated positions, it is well to keep in mind the 


weight of water and to see that the supports 
are amply strong. For example, a lo-barrel 
tank of water will weigh, in addition to the 
tank itself, more than one and a quarter 

The pressure to be obtained from elevated 
tanks depends upon their elevation, each ad- 
ditional foot giving a pressure of about 0.433 
pounds per square inch. The following table 
shows the pressure (disregarding friction) 
to be obtained at various heights. 

Height in feet Pressure per sq. inch 

10 4.33 pounds 

20 8.66 

30 12.99 

40 17.32 

50 21.65 

60 25.98 

70 30.31 

80 .' 34.64 

90 38.97 

The advantage of the pneumatic tank lies 
in the fact that it may be placed in any out- 
of-the-way place in the basement, or it may 
be buried in the ground below the frost line. 
There is little danger in its use is pro- 
vided with a pressure gauge and safety valve. 

Capacity of Storage Tanks. — The capac- 
ity of storage tanks is not difficult to arrive 
at by simple mathematics, unless they are 


of unusual shapes. For. convenience, tables 
are given below showing the capacity of 
round and square tanks of standard sizes. 
When pneumatic tanks are used, about a 
third of their capacity is occupied by the 
compressed air. 


Diameter Height Capacity Diameter Height Capacity- 
Feet Feet Gallons Feet Feet Gallons 












































Width Height Length Capacity 

Feet Feet Feet Gallons 
























































There are two general methods of water- 
ing greenhouse crops aside from hand water- 
ing. One is by an overhead sprinkling sys- 
tem ; the other is by an underground or sub- 
irrigating system. Of these the overhead 
. system is by far the more popu- 

I lar. A census of a large number 

of growers of greenhouse vege 
tables shows that practically 75 
per cent, use some form of over- 
head irrigation, while only two 
out of the whole number con- 
sulted were using sub-irrigation. 
Practically the only system of 
overhead irrigation used in 
greenhouses is one in which 
pipes, fitted with nozzles which 
Fig. 125 — A throw a rain-like spray, are run 

type of nozzle - . , • r . t. f i 

used in over- lengthwise of the house and so 
head irrigration arranged that they may be rotat- 
ed to throw the spray on both sides of the pipe 
line. The original system is known as the 
Skinner system, but there are others now 
on the market. Pipe lines for this system 
should be about 16 feet apart and as far from 
the foliage as possible. The nozzles should 
be 3 feet apart. This system will operate 



satisfactorily on ac water pressure of from 
10 to 30 pounds. 

When constructing benches for sub-irriga- 

Fig. 126. — Greenhouse bench arranged for sub-irrigation. 
A, cement troughs on bottom of bench; B, drain tile or 
perforated pipes for supplying water; C, drainage spaces 
between troughs. 

tion, the essentials are a water-tight bottom, 
usually of cement, to prevent the water from 
leaking through, and perforated pipes or tiles 
for distributing it along the bench. This 
system has been tried out extensively with 
varying results by the Ohio experiment 


Concrete is a combination of Portland 
cement, sand, crushed stone or gravel and 
water, thoroughly mixed and then allowed 
to set or harden. 

Portland cement, or cement, as it is now 
commonly known, is manufactured by burn- 
ing and grinding together- limestone and 
clay, or shale, in certain proportions. It de- 
rives its name, Portland cement, from its re- 
semblance to Portland stone. It is also 
sometimes known as hydraulic cement, or 
building cement. 

Concrete has wellnigh revolutionized 
building practice in the last 25 years, but in 
no case has it displaced masonry to a greater 
extent than in greenhouse construction. 
Formerly, the walls of a greenhouse were a 
source of much trouble, because of their 
rapid deterioration, but it was soon found 
that when concTrete was used they be- 



came the most stable part of the structure. 
Concrete is practically the only material now 
used for the foundations and walls of com- 
mercial greenhouses, and to a great extent 
it has displaced masonry for private 

At present cement is almost universally 
handled and shipped in cloth or paper sacks 
holding 95 pounds. It is often spoken of, 
and is sometimes quoted by the barrel, *this 
now meaning simply four sacks, or 380 
pounds. As a rule, the most satisfactory 
form in which to buy cement is in cloth sacks. 
The sacks may be returned when empty, and 
if not torn a credit of about 10 cents each 
may .be realized. 

Sand. — Sand, to give the most satisfac- 
tory results, should be free from clay or or- 
ganic matter, and rather coarse. Very fine 
sand will require a greater proportion of 
cement and aa a consequence the concrete 
will be more expensive. In a small way, 
sand that contains some organic material 
may be washed and thus made satisfactory, 
but it is an expensive process. 


Stone. — Either crushed stone or gravel 
may be used in making concrete, the only 
difference being that the crushed stone usual- 
ly has a cleaner surface and the cement will 
cling to it more tightly. When gravel is 
used it should be free from clay, and the in- 
dividual stones^ should be clean and bright 
and not covered with a layer of clay or soil. 

The size of the stones may range from a 
fourth to two and a half inches in diameter, 
the size depending on the use to which the 
concrete is put. The best results are ob- 
tained when the sizes vary regularly from 
small to large, in order that they may settle 
well together when the concrete is poured. 

Run of the Bank gravel is sometimes used. 
This is economical only when it contains 
sand and gravel in the correct proportions, 
as explained in a succeeding paragraph. 

Crushed Stone may also contain very fine, 
medium and coarse stone in the correct pro- 
portions, so that no sand need be added, but 
such a condition is rare, unless tlie stone is 
ground and furnished for this special pur- 


Proportions of Materials. — Theoretically, 
the ideal concrete is a mixture in which all 
the spaces between the stones or gravel are 


Fig. 127. — Proportions of cement, sand and stone re- 
quired to form concrete 

filled with sand, and all the spaces between 
the grains of sand are filled with cement. 
From this it will be seen that the total bulk 
of concrete would not be greatly in excess 
of the bulk of stone or gravel, as the sand and 
cement would go to fill the vacant spaces 
(voids). This is really true except that, as 
usually proportioned, a slight excess of ce- 
ment is allowed. This is wise in order to 
insure that ther^ shall be a film of cement 
about each stone and grain of sand, so they 
may be all bound together in a solid mass. 
The common formula for most concrete 
work is known as the i :2 4 mixture. In this 
there are: i part by measure of cement, 2 
parts of sand, and 4 parts of stone or gravel. 


This is the formula commonly used for walls 
above ground and for bridges and similar 
work. For sidewalks, floors, etc., which are 
supported on a firm foundation and are not 
subjected to heavy strain, a weaker mixture 
of I part of cement, 2/4 parts of sand and 5 
parts of stone or gravel, is sometimes used. 
For plastering the outside of walls and for 
similar purposes a mixture of cement and 
sand alone in the proportion of i to i is used, 
as it is easily worked and leaves a smooth 

Mixing. — For small jobs concrete is 
usually mixed by hand. The essentials are : 
(i) A tight platform or mixing board of suf- 
ficient size; (2) a convenient measuring box; 
(3) suitable shovels; and (4) a supply of 
water. Quite commonly the sand and gravel 
is measured in the wheelbarrows in which 
it is hauled, a little experience, secured by 
carefully measuring the amount for a few 
times, being all that is necessary to insure 
sufficiently accurate measuring. The bar- 
row loads are checked up from time to time, 
however, to see that they are not over-run- 
ning or falling short. 


It is convenient to mix in batches requir- 
ing even bags of cement. For example, a 
two bag batch would mean two bags of ce- 
ment, a quantity of sand equal to 4 bags 
(3^ cubic feet) and 8 bags (7/4 cubic feet) 
of stone or gravel. They are mixed together 
thoroughly, shoveling over several times be- 
fore adding the water. 

Amount of Water. — The quantity of water 
used has but little effect on the resulting con- 
crete, the amount depending rather on the 
consistency at which the concrete can best 
be handled for the special purpose for which 
it is to be used. The dryer the mixture the 
more quickly it will set. 

For thin walls, or where the form con- 
tains many indentations, the mixture should 
be thin enough to run off the shovel quickly 
in handling. 

For walls of medium thickness (6 to 12 
inches) or for floors, walks, etc., it should be 
jelly-like in consistency, so that it will pile 
up somewhat on the shovel, but will slowly 
settle and run off the sides. 

For foundations, underground, where it is 
important that the mixture set as quickly as 


possible, it may be mixed so dry that it will 
handle like damp earth. Care must be taken 
in making this "dry mixture'' that every part 
is moistened. 

Estimating Materials. — The quantity of 
cement, sand and gravel necessary for a giv- 
en piece of work may be found by multiply- 
ing the number of cubic feet by the percent- 
age of cement, sand and gravel in a cubic 
foot of the mixture to be used. For con- 
venience these proportions are given in tabu- 
lar form in terms of barrels of cement and 
cubic yards of sand and gravel. 


Cement Sand Stone or gravel 

Mixture barrel cubic yard cubic yard 

1:2 :4 0.058 0.0163 0.0326 

1:25^:5 0.048 0.0176 0.0352 

To use, multiply the number of cubic feet 
of concrete required by the factor shown in 
the table. The result will be the quantity of 
the material required. 

For example, looo cubic feet of 1:2:4 con- 
crete would require 


1000 X 0.058 or 58 barrels of cement 
1000 X 0.163 or 16.3 cubic yards sand 
1000 X 0.0326 or 32.6 cubic yards gravel 
In estimating for cement mortar, figure i 
cubic foot to each 15 square feet of surface to 
be covered. Each cubic foot of i :i sand and 
cement mortar requires 0.1856 barrels of ce- 
ment and 0.0263 cubic yards of sand. 

Forms.^-As concrete is soft when mixed, 
it is necessary to have some kind of a form 
or mold to hold it in the desired form and 
position until it hardens. For foundations, 
for such structures as greenhouses, a trench 
is usually dug 12 or 14 inches wide, and deep 
enough so that the bottom will be below 
the frost line. If the soil is firm enough to 
hold its place no form will be needed, but 
the concrete may be poured directly into the 
excavation, tarhped and allowed to harden. 

For that part of the wall which is above 
ground, however, a form is needed. It is 
important that this form be vertical, that 
it be straight, and that it be smooth in tlie 
inside so that the resulting wall will be agree- 
able to the eye. The making of the forms is 
important. They should be built by an ex- 
perienced carpenter. 



Any kind of lumber which is free from 
knot holes and has been surfaced to an even 
thickness will answer for forms. If the wall 
is a high one it may be necessary to tie the 
sides of the form together with wire. The 
wires remain in the concrete when the form 
is removed, but may be cut off flush with the 
surface, and if the wall is plastered they will 
not be noticed. 

I -■ 
Fig. 128. — Form for a concrete wall 



Filling the Forms. — In filling- the form the. 
concrete is placed in layers about 6 inches 
deep and tamped lightly until water shows 
on the surface. This will 
insure its settling together 
closely- If the wall is not 
to be plastered and a smooth 
surface is required, a spade 
or paddle is run down all 
along between the concrete 
and the sides of the form 
when the concrete is poured. 
This will force the larger 
stones toward the center of 
the wall and allow the 
smaller stones and sand to 
fill in next to the form, thus 
making a smooth surface. 

Reinforcing. — Concrete 
will withstand enormous 
crushing loads, but in walls where there 
is a considerable side strain, it should be 
reinforced with iron or steel. The best 
materials for this purpose are iron or steel 
rods. If they are twisted or roughened in 
some manner, so that the concrete will ad- 
here to them tightly, their efficiency will be 
greatly increased. They are put in the 

Fig. 129.— Meth- 
od of facing a 
concrete wall 


forms, usually vertically, about midway be- 
tween the sides and 2 or 3 feet apart before 
the concrete is poured. 

When an extra strong wall is required rods 
may be laid horizontally on the top of every 
layer or every second layer as the concrete is 
placed and tamped down into the soft mix- 
ture. When the walls extend only 3 or 4 feet 
above the surface and are at least 8 inches 
thick as is commonly the case in greenhouses, 
little if any reinforcement is needed. 

Walks and Floors. — Concrete walks are 
now very commonly used in commercial as 
well as private greenhouses, and the boiler 
and service rooms are usually floored with 
concrete. As the walks are not usually sub- 
ject to as hard usage as those laid out-of- 
doors, or to the action of frosts, it is not 
necessary to make them quite as thick, but in 
other respects they differ but little from the 
concrete sidewalks now so common. 

The common method of building walks in 
a greenhouse is to make an excavation a few 
inches deep and as wide as the walk is to be 
and fill it with broken stone, pieces of brick, 
etc., to make a foundation. On top of this, 
two pieces of straight 2 x 4-inch lumber are 
placed on edge, level with each other and 


with their inside edges spaced just as far 
apart as the walk is to be wide. They are 
then fastened by driving stakes on the out- 
side and nailing. The concrete is then 
poured into this form to within about an inch 
of the top and tamped firmly. A top coat, 
usually of finer material, is then placed on 
top of the first layer before it is set, and 
struck off by running a straight edge along 

Fig. 130. — Structure of a concrete walk, a, foundation; 
b, coarse concrete; c, finish coat of fine concrete 

the tops of the side pieces. This is then 
troweled by hand to give a smooth and 
slightly curving surface. 

To allow for expansion and contraction, 
the walk should be cut into blocks before it 
sets. This may be done by putting in pieces 
of thin sheet-iron at regular intervals to be 
removed when the " concrete has partially 
hardened. Sometimes the walk is cut 
through with a spade while still soft, at regu- 
lar intervals and fine, dry sand placed be- 
tween the blocks so made. This is usually 
quite satisfactory and by careful troweling 


a very neat walk may be made in this way. 

For the lower layer, when there is a firm 
foundation, a 1:2/^:5 mixture will be satis- 
factory. The top layer should be of a i :2 14 
mixture or, when an especially smooth sur- 
face is required, of a i :2 mixture, that is, 
one part of cement and two parts of sand. 

Floors are laid >practically the same as 
walks, except that they are usually troweled 
level instead of curving. The work is begun 
at one side of the floor, and as soon as one 
section has been laid and has had time to 
set, the side boards are taken up and put 
down for the next section. Floors should 
seldom or never be laid in a solid mass. 

Waterproofing. — Much trouble is often 
experienced in underground boiler rooms 
from water. The best protection is to lay 
a row of tile completely around the 
outside of the foundation, at the bottom, and 
connect it with the sewer or drain. If the 
bottom of the cellar is springy it may be 
necessary to lay the floor in a solid piece and 
in two layers. After the first layer has set 
and become dry, or nearly so, a thick coating 
of hot tar may be applied, allowing it to ex- 
tend for a few inches up the side walls. 
When this has hardened put on another coat 


of rich concrete, troweling it up the sides 
as far as the tar has been placed. When an 
absolutely watertight job is required it may 
be necessary to coat the entire outside sur- 
face of the walls with tar and then bank up 
with earth. 

Several so-called waterproofing materials 
designed to be placed in the concrete when 

Fig. 131. — A small power machine for mixing concrete 

it is mixed are on the market, but as a rule 
they are not fully satisfactory. 

Concrete Blocks. — Blocks made of con- 
crete in special molds or forms are sometimes 
employed for walls. They are usually hol- 
low and for that reason make a warmer and 
somewhat dryer wall than does solid, poured 


concrete. Experience shows that as a rule 
they are less durable than solid walls, but 
when the cost of material and labor for mak- 
ing forms is considered they may be more 
economical. They are often made with an 
ornamental face resembling broken stone, 
and make a somewhat more pleasing appear- 
ance than a plain wall. 

Cost of Concrete. — So many factors enter 
into the cost of concrete that no reliable 
general estimate can be given. The price of 
cement is now fairly constant and uniform. 
The cost of sand and gravel or crushed stone, 
on the other hand, differs widely. In some 
places it may be had on the premises, in 
others it may have to be transported for 
several miles. Other factors entering into 
the cost are labor and the size of the opera- 
tion. Where the quantity of work will justi- 
fy the use of a power mixing machine, the 
cost is usually less than when the mixing is 
done by expensive hand labor, although the 
cost for labor may often be greatly reduced 
by carefully planning the work. 

In general the contract prices for walls on 
comparatively small jobs range from 7 to 20 
cents per cubic foot, and for walks and floors 
from 4 to 15 cents per square foot. 



The cost of any kind of a building must 
necessarily vary with the cost of building 
material and the price of labor. This is es- 
pecially true with greenhouses, since the ma- 
terials used (glass especially) are subject 
to extreme fluctuations in price. In the pre- 
ceding chapters it has been the aim to give 
all the data necessary for estimating the 
amount of material required for any given 
house, but no attempt has been made to state 
definite prices. 

Little can be added in this chapter to what 
has already been given, and it would be use- 
less repetition to collect the data into one 
chapter, as it may be easily found by refer- 
ring to the index. An effort has been made, 
however, to make some suggestions as to the 
probable cost of different types of houses un- 
der varying conditions. 

Basis of Estimates. — Since the economic 
value of a greenhouse depends on the area of 



surface covered (bench space) it is common 
to estimate costs in terms of square feet of 
surface covered. In an investigation among 
a large number of growers (all types of 
houses) the author found that the first cost 
averaged not far from 45 cents per square 
foot of surface under glass. This included 

cost of heating system, but did not include 
cost of service buildings. 

The cheapest plant on which data was se- 
cured was a range of four all wood frame 
houses, 16 X 50 feet, which had been in serv- 
ice for nine years and which was built at a 
cost of $525, or about 22 cents per square 
foot. In this case a second-hand boiler was 
used. Several larger ranges heated by steam 
from a central heating plant have been built 
at a cost of between 30 and 40 cents per 
square foot, though at a time when material 
was low in price. Data on modern semi- 
iron construction, when the labor was per- 
formed for the most part by the owner and 
his help, show a cost of between 50 and 60 
cents per square foot, and all iron construc- 
tion between 60 and 75 cents per square foot. 
All these, of course, were standard commer- 
cial houses. Private and public conserva- 


tories and ornamental houses often cost two 
and three times as much. 

Detailed Estimates. — Detailed estimates 
necessarily differ with the grade of material 
used. The following is a detailed estimate 
at current prices of the material needed for 
and the cost of a sem-iron frame house 
30 X 90 feet, not including labor of erecting. 

850 cubic feet concrete Cwall and piers) — 
50 barrels cement 
14 cubic yards sand 
28 cubic yards gravel $100 

Side Posts — 

32 pieces 2-inch pipe, 5 feet 6 inches 
Purlins — 

360 feet Iji inch 
Purlin Supports — 

24 pieces 1^-inch pipe, 8 feet 3 inches 

24 pieces lJ/2-inch pipe, 11 feet 
Cross Ties — 

24 pieces 1^-inch pipe, 5 feet 

24 pieces T^-inch pipe, 8 feet 6 inches 
Pipe and fittings for water lines, 100 feet H inches $75 


32 Gutter brackets 
120 Clamp fittings 

48 Foot pieces 
140 Purlin clasps $30 

240 feet sill 
180 feet eave plate 


90 feet ridge 
180 feet drip gutter 

4 pieces gable rafter, 18 feet long 
268 pieces sash bars, 18 feet long 

4 pieces corner bars, 4 feet long 
268 pieces glazing bars, 4 feet long 
180 feet sash header 
330 feet glazing bar 
100 feet 2x4 for door casing and gable bracing 

1 door 
Ventilator sash -with stops $200 

86 boxes glass (16x24) 
500 pounds putty 

8000 glazing points $250 

Ventilating apparatus $25 

Nails and other hardware $25 

Paint $50 

Freight $15 

Miscellaneous items $25 

Boiler (hot water) 
Pipe and fittings 
Brick for flue $550 

Total $1345 

This house covers approximately 2700 
square feet of surface, which at a cost of 
$1,345 gives a cost per square foot of 49.81 
cents for materials, but not including labor. 

Figures on a similar house 31 x 100 feet 
submitted by a well-known manufacturer of 
greenhouse materials are given below: 


200 feet gutter with drip 
100 feet ridge 
228 feet glass sill 
175 feet gable end bars 

4 pieces ga'ble rafters, 18 feet long 
144 pieces sash bars, 18 feet long 

12 ventilators 

12 pieces ventilator sash cap 
60 headers 
144 side bars 

4 corner bars 

1 door $177.01 

Ventilating machine complete $26.40 

Hinges for ventilators 3.60 

Trussing nAiterial 5.20 

Hardware for doors .63 

40 pieces 2-inch, 5 feet long 
40 pieces post tops $27.20 



10 pounds glazing paints 


400 pounds putty 




Glass, 4600 square feet 


Purlins, fittings and purlin 



Gable bracing material 


Heating plant complete 




The latter estimate does not include cost 
of materials for walls, but in other ways is 
complete. The cost per square foot of sur- 
face covered is 43.9 cents not including wall 
and cost of erection. 


For an all wood frame house the cost of 
material will probably be from 15 to 25 
per cent, less than the above and •the cost of 
erection from 10 to 20 per cent. less. 

For an all metal frame house the cost for 
materials will range from 25 to 40 per cent, 
greater than for the semi-iron construction, 
but the cost of erection will be less. 

Information Required for Estimates. — In 

writing for estimates the following informa- 
tion should be given : 

1. Type of house (semi-iron, all metal, 

2. Kind of roof (even span, three quarter 
span, etc.). 

3. Length and width (if range, send 
sketch showing arrangement). 

4. Height to eaves. 

5. Pitch of roof or height to ridge. 

6. Size of glass preferred. 

7. Kind of heat (hot water, steam, vapor). 

8. Temperature to be maintained. 

9. Coldest outside temperature expected. 

10. Kind of fuel (hard or soft coal). 


All-metal frame greenhouses 

Asbestos covering for furnaces and pipes 


Beds (greenhouse) 

curbs for 

of hollow building tile 

arrangement of 


for sub-irrig'ation 

height and width of 

iron frame 


accessories for 

arrangement for steam 

cast iron 

essentials of . 

hot water 

for hard and soft coal 

ratings of 

self stoking 


styles of cast iron 

styles of wrought iron 

types of . 


wrought iron 

Cast iron boilers . 
Chimneys and flues 

size and height of 

cost of . 

heating value of 

kinds of . 








Coils (heating) . 

arrangement of . . - 

length of for hot water heating 

length of for steam heating 
Coldframes .... 


construction of 
Cold-pits . . , • 

Concentric system of framing 
Concrete construction . 

blocks .... 

cost of . . . 

estimating materials 

filling forms . 

forms for . . • 

mixing .... 

water needed for . 

water proofing 


Curved eave construction 
Curved roof greenhouse 
Cypress (pecky) . 









Double glass sash 
Drip gutter . 


Eave plate . . • • 
Even span greenhouse . 
Expansion tank 

Fire surface of boilers . 
Flow pipe, how to find size of 

size and height of . 
Forcing boxes 
Forcing houses 

classes of . • • 

Framing . • • • 

Fuels .. . . • • 



181, 187 








Gable rafter 





Gable roof sash-bed 30 

Gearing, ventilator 



grades of . 


quantity in box 


sizes of . 


substitutes for 




butted method 


lapped method 


window and greenhouse 


Glazing bars . 


Glazing points 


Glazing ladders 


Glazing sill .... 

... 65 

Grate surface 



architecture of 


arrangement of 


circular . . 

. . . . . 62 

curved eave 


curved roof 


erection of 


even span 


evolution of 


framing . 


glass for 






location of 


plans and estimates for 




side hill . 


size of . . . 


structural material for 

... 63 

ventilation of . 


uneven span . 


Gutter .... 



Hanging rail, sash 76 

Heat, loss by reflection 


Heating, greenhouse 


by hot water . 


by steam .... 


coils .... 

. 164, 179, 191 

combination sj 





principles of . 

hot water vs. steam 

with cast iron pipes 

with flues . . 

High pressure steam heating 

construction of 


heating by flues 

location for 

manure for 

permanent, plans for 

sash for . 

temporary, plans for 
Hot water heating 

advantages of 

arrangement of pipes for 

estimating radiation for 

general principles of 

pipe for .... 

pressure systems 















169, 178 

171, 176 






loss by absorption 

loss by reflection 

for greenhouses 

for hotbeds 

Mats, sash-bed 
Manure for hotbeds 






for iron work 
for shading 
kinds of . 

Painting • . 

"Pecky" cypress 







covering for . 




paint for 




wrought iron 


Pit for hotbed 


Pitch of roof 


Plans and estimates 


basis of . . ... 


detailed estimates for greenhouses 


information required for 


Plant forcers ...... 


Pressure systems of hot water heating . 


Propagating house 



capacity of ..... . 


for circulating hot water 


kinds of . 


power required for 




Purlins . . . . . 








Putty bulb 


Radiation, how to estimate .... 




Rams, hydraulic 


capacity of 


double acting ...... 


plan for installing ..... 


Range of glass, a . 




Ridge-and-furrow houses .... 


Roof, pitch of 


Sash . . 


cost of 


glazing of 


kinds of ...... . 




Sash-bars • 


spacing of . . . . ,» . 




attached to dwelling ..... 28 

classes of ... . 


gable roof .... 


materials, care of *. 


Sash sill 


Semi-iron frame houses 


Shading „ 



Shaft hangers .... 


Shafting, ventilator 


Shed roof greenhouse . 




Side hill greenhouse 


Side ventilating machinery . 

126, 134 

Sliding shaft ventilating machine 


Steam heating .... 


advantages of 


arrangement of boilers for 


arrangement of coils for 


coils for . 


general principles . 


high pressure .... 


vacuum and vapor systems 


Steam pumps and traps 


Stove house . . 


Structural material 


Substitutes for glass 



capacity of . ... . . 238 


181, 187 

height of 


types of 


Traps, steam return .... 


Truss framework 



Uneven span greenhouses 


Vacuum systems of heating 
Vapor systems of heating 
Ventilation . 



systems of 







arms for .... 

. 136,138 

header ..... 

, . . U 

methods of hanging 


size of * 


Ventilating machinery 

capacity of . . 


chain system .... 


closed column 




open column .... 


rack and pinion 





. 134,136 

sliding shaft ..... 




ashes used for ... 


concrete ..... 


construction of 


materials for . 


width of 



. 83,251 

Water supply 

amount used in greenhouses . 


cost of^ 


hydraulic rams for raising 


pumps for 

. 227 228 

storage tanks for 


Waterproofing for concrete 


Weather strip .... 


Wood, kinds used in g^reenhouse construction . 17 

Wood frame grreenhouses 


Wrought iron boilers . . 


Wrought iron pipe .... 



YB /^8587 





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